The drag learns the stepper's trick — past the screen's edge, lane growth re-divides instead of stopping

The right-edge drag's growth was capped at the screen's visible frame,
because each snap tick grows the window; on a window near the screen edge
that left a lane stuck at a tick or two of headroom. Settled 2026-08-08
(03-board-ui.md § Lane, superseding the pathfinder's hard stop): at the
screen the window pins and each further tick re-divides the fixed strip
width across one more unit — siblings compress, the stepper's mechanism
arriving under the drag's fingers. The regimes meet with no pixel jump
(the re-divided standard at the fit IS the frozen standard, by the
exact-fill identity), shrinking mirrors the way back, the rubber band
moves to the strip's own capacity, and a window with no headroom at all —
full screen included — re-divides from the very first snap.

New pure arithmetic in LaneLayoutMath (pinnedStripWidth, resizeStandard,
resizeMaxUnits, resizeWindowDelta, snappedUnits over per-count slots);
LaneResizeSession splits the tick across the regimes and derives its
standard from the live count; the handle and BoardView hand the session
the strip's whole divide. 2709 unit tests green (+11).

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

DESIGN/03-board-ui.md

@@ -20,7 +20,7 @@ Toolbars are **pure enhancement**: every function they host already has a menu i
 
 - 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.
 - 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. **Growth hard-stops at the screen's visible frame, with rubber-band feedback** (the dragged edge gives a fraction of the overshoot and snaps back, signalling the bound — pathfinder behavior, proven): the drag never compresses siblings and the window never overflows the screen. The header context menu's Width control (stepper, uncapped) is the precise control — and deliberately the opposite mechanism: it never touches the window, it **re-divides** the existing width across the new unit total (siblings compress). Widths beyond the screen's capacity stay reachable through it. 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.
+- 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.
 
 ## Card face