Remove the lane header's "+" new-card control

The lane header no longer draws a new-card button. Every other
creation path is untouched: File > New Card (Cmd-N), Return on a
selected lane, and double-click on lane empty space.

- LaneView: drop the button and its overlay slot, leaving the
  collapse chevron as the header's one piece of trailing chrome.
- NewCardTarget: drop the button's click-names-target carve-out over
  the Cmd-N target rule (Return on a selected lane is now the only
  direct-target path left).
- AccessibilityPhrases: drop the button's spoken label.
- BoardMetrics: drop its width reserve; laneHeaderTrailingReserve now
  reduces to the collapse chevron's own reserve.
- DESIGN/03, 04, 10, 11: update the lane title-bar inventory, the
  Cmd-N override clause and search-clearing mechanism list, the
  accessibility tree-shape sentence, and the pointer-grammar row that
  described the button.
- Tests: drop the two pinned accessibility-label tests and the
  newCardButtonReserve assertions; retarget the truncation-headroom
  test at the now-solo laneHeaderTrailingReserve; fix stale doc-quote
  comments and the manual accessibility-verification checklist.

Full KanbanTests suite: 2807 tests, 482 suites, all passing.

Claude-Session: https://claude.ai/code/session_014PtZdPwqZuqEDLc6wZMtEy

DESIGN/03-board-ui.md

@@ -18,10 +18,10 @@ Toolbars are **pure enhancement**: every function they host already has a menu i
 
 ## Lane
 
-- Title bar: leading SF Symbol (the lane's `icon`), title, **card-count badge** (quiet, secondary styling), new-card button. The whole title bar is the lane's drag surface — no separate grip; a plain click (no movement) on it selects the lane (04-interactions.md ▸ Selection). **The lane has one context menu** (settled), invoked on the header or on lane empty space alike — Rename, Style…, the quick-style recents row, the Width stepper, Delete (inventory normative in 11-command-nexus.md ▸ Context menus); a full lane still has its header, so the menu is always reachable. The count reads the search filter like every other surface (04-interactions.md): during a search it shows the visible count, not the total.
+- Title bar: leading SF Symbol (the lane's `icon`), title, **card-count badge** (quiet, secondary styling), the collapse chevron (below). The whole title bar is the lane's drag surface — no separate grip; a plain click (no movement) on it selects the lane (04-interactions.md ▸ Selection). **No header card-creation control** (removed): the header carried a "+" new-card button through m5; it is gone, and every other creation path — ⌘N, Return on a selected lane, double-click on lane empty space — is unchanged. **The lane has one context menu** (settled), invoked on the header or on lane empty space alike — Rename, Style…, the quick-style recents row, the Width stepper, Delete (inventory normative in 11-command-nexus.md ▸ Context menus); a full lane still has its header, so the menu is always reachable. The count reads the search filter like every other surface (04-interactions.md): during a search it shows the visible count, not the total.
 - Body: vertical card stack (masonry grid when wide — settled, the pathfinder's masonry works), scrolls vertically.
 - Right-edge **drag-to-resize** between integer widths (1×, 2×, 3×, … — no cap): shadow snaps at the inter-column gap with 10pt release hysteresis; the window grows/shrinks by one standard width per snap so other lanes keep their exact size. **At the screen's visible frame the window stops and the drag degrades to the re-divide** (settled 2026-08-08, superseding the pathfinder's hard stop): further snaps re-divide the now-fixed width across one more unit each — siblings compress, exactly the stepper's mechanism — so a lane keeps growing at the siblings' expense once the screen is spent; a window with no headroom to begin with (already at the edge, or full screen) re-divides from the first snap. The two regimes meet without a pixel jump — the re-divided standard at the screen fit *is* the frozen standard. Shrinking mirrors it: re-divide back down to the screen fit, then window shrinking resumes (and shrinking is always allowed). The rubber-band feedback (the dragged edge gives a fraction of the overshoot and snaps back, signalling the bound) moves to the true end of travel — the strip's own capacity — and the window still never overflows the screen. The header context menu's Width control (stepper, uncapped) remains the precise control: it never touches the window, it **re-divides** the existing width across the new unit total (siblings compress); the drag now reaches those widths too, but the stepper stays the exact, accessible path. The **Increase/Decrease Lane Width menu items (⌥⌘→/⌥⌘← — 11-command-nexus.md) are this stepper's keyboard face** — same re-divide semantics, never the window's size; window-growing behavior belongs to the drag alone — and they **batch over a multi-lane selection** (settled, the styling precedent): each selected lane steps one unit, one gesture, one commit; the context-menu stepper itself stays single-lane by nature. **A width write landing on 1 removes the `width` key** (settled — the remove-at-default family: the empty rename removes `title`, the None well removes `background`): a default lane's frontmatter stays clean, drag, stepper, and menu items alike; a hand-written `width: 1` is legal and preserved until the app itself next edits width. **A failed width commit at drag release rolls the window back** (settled): the failure surfaces as the ordinary one-shot banner and the window animates back by the uncommitted delta — 02-architecture.md's write-failure honesty (the action visibly doesn't happen) applied to the one control that moves the window.
-- **Collapsed lanes** (settled 2026-08-08): a lane folds to a **fixed slim vertical strip** — its `icon`, its card-count badge, its title rotated a quarter turn **counterclockwise so it reads bottom-up** (the book-spine orientation) and **justified to the top** of the room below that chrome (ruled by the owner 2026-08-08, reversing the top-down reading of the first pass), and its accent band, at a fixed width (~44pt, an em multiple like every other figure) — and **the strip is not part of the width re-division**: the window's width divides across the *expanded* lanes' units alone, with each collapsed strip's fixed width taken off the top, so folding a lane is a re-divide trigger of the Show/Hide Trash family (the window never moves and the siblings grow into what the lane gave up). Persistence is a first-class lane frontmatter key, `collapsed: true` — **document state exactly like `width`**, because the files are the board and an agent must be able to fold a lane by editing frontmatter; absent means expanded, expanding **removes** the key (never writes `false` — the remove-at-default family), and the lane's `width` is preserved untouched while collapsed so expanding restores the lane the user had. **Toggling**: the header's trailing collapse chevron (always visible beside the new-card button — the header has no hover chrome to match), the lane context menu's single **Collapse Lane** / **Expand Lane** row (single-lane like the width stepper, not batched), and a plain click anywhere on the collapsed strip, which expands it; a modified click on the strip stays the ordinary selection grammar, so a folded lane is still selectable by pointer. Rename and the expanded header's double-click behaviours are unchanged. **While collapsed**: no resize handle (the width stepper and ⌥⌘→/⌥⌘← still edit the preserved key), and the lane's cards are **not rendered at all** — which is what excludes them from the marquee sweep, from spatial keyboard navigation, and from the ⌥-arrow jumps (↓ from a folded lane is inert, like an empty one), and what makes ⌘N skip the lane for creation (a selection inside a folded lane falls through to the last-active lane rather than refusing). A drop on the strip **appends at the lane's end**, like an end-of-lane drop, with an accent edge standing in for the shadow the strip has no masonry to open; there is no hover-to-auto-expand in v1 (future work). Lane reorder drag works on the strip, and a folded lane's replica and drop shadow are the strip rather than its units. **Search still matches cards in collapsed lanes** — the badge and the flatten lists count them, since collapse is a presentation fold rather than a filter — but the lane stays folded and shows no match: pointing into a folded lane is not something the current search presentation can do, and the honest minimum is that the query does not fold or unfold anything. The **trash quasi-lane is not collapsible**; multi-select styling and the Style editor are unaffected.
+- **Collapsed lanes** (settled 2026-08-08): a lane folds to a **fixed slim vertical strip** — its `icon`, its card-count badge, its title rotated a quarter turn **counterclockwise so it reads bottom-up** (the book-spine orientation) and **justified to the top** of the room below that chrome (ruled by the owner 2026-08-08, reversing the top-down reading of the first pass), and its accent band, at a fixed width (~44pt, an em multiple like every other figure) — and **the strip is not part of the width re-division**: the window's width divides across the *expanded* lanes' units alone, with each collapsed strip's fixed width taken off the top, so folding a lane is a re-divide trigger of the Show/Hide Trash family (the window never moves and the siblings grow into what the lane gave up). Persistence is a first-class lane frontmatter key, `collapsed: true` — **document state exactly like `width`**, because the files are the board and an agent must be able to fold a lane by editing frontmatter; absent means expanded, expanding **removes** the key (never writes `false` — the remove-at-default family), and the lane's `width` is preserved untouched while collapsed so expanding restores the lane the user had. **Toggling**: the header's trailing collapse chevron (always visible, not hover-revealed — the header has no hover chrome to match), the lane context menu's single **Collapse Lane** / **Expand Lane** row (single-lane like the width stepper, not batched), and a plain click anywhere on the collapsed strip, which expands it; a modified click on the strip stays the ordinary selection grammar, so a folded lane is still selectable by pointer. Rename and the expanded header's double-click behaviours are unchanged. **While collapsed**: no resize handle (the width stepper and ⌥⌘→/⌥⌘← still edit the preserved key), and the lane's cards are **not rendered at all** — which is what excludes them from the marquee sweep, from spatial keyboard navigation, and from the ⌥-arrow jumps (↓ from a folded lane is inert, like an empty one), and what makes ⌘N skip the lane for creation (a selection inside a folded lane falls through to the last-active lane rather than refusing). A drop on the strip **appends at the lane's end**, like an end-of-lane drop, with an accent edge standing in for the shadow the strip has no masonry to open; there is no hover-to-auto-expand in v1 (future work). Lane reorder drag works on the strip, and a folded lane's replica and drop shadow are the strip rather than its units. **Search still matches cards in collapsed lanes** — the badge and the flatten lists count them, since collapse is a presentation fold rather than a filter — but the lane stays folded and shows no match: pointing into a folded lane is not something the current search presentation can do, and the honest minimum is that the query does not fold or unfold anything. The **trash quasi-lane is not collapsible**; multi-select styling and the Style editor are unaffected.
 
 ## Card face