replace symbol grid in card window sidebar with a compact symbol picker

The card window sidebar's Style section embedded StyleEditorView symbols-only
(showsBackground: false, showsSymbols: true), drawing the curated grid whole
inside the sidebar's own scroll view — a permanently open 5-7 row grid ahead
of every other section. Replace it with the reusable compact SymbolPicker
(already used by BoardInfoPopover for the board's glyph): a single well at
rest, the grid only inside its own popover.

- CardStyleSection no longer instantiates StyleEditorView at all. A new
  "Symbol" row mirrors the existing "Background" row's inspector shape
  (caption leading, control trailing), wiring SymbolPicker's onSelect/
  onSelectColor to icon/iconColor through StyleCommand.apply(...on: undo),
  the exact funnel the background combo already rides — so the card window's
  undo session semantics (13-native-undo.md) are unchanged.
- The picker is fed CuratedSymbols.available rather than its own smaller
  general-purpose default, so a card's curated vocabulary doesn't shrink.
- StyleEditorLayout.sidebar and showsBackground stay in StyleEditor.swift
  (still correct, still tested) rather than being cut as dead code — a
  separate, larger cleanup this card doesn't make (recorded on the card).
- DESIGN/03-board-ui.md and DESIGN/05-card-window.md: updated the sentences
  describing the sidebar hosting the style editor's symbol grid to describe
  the compact picker instead.
- Tests: CardSessionUndoTests gains a symbol/tint analogue of the existing
  background-combo session-routing test; CardSidebarTests gains a curated-set
  tripwire and an updated file-header note.

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

DESIGN/03-board-ui.md

@@ -41,7 +41,7 @@ Toolbars are **pure enhancement**: every function they host already has a menu i
 
 ### Controls (settled)
 
-One **style editor** component — a background palette grid and a curated symbol grid — presented from two anchors: **embedded** in the card window sidebar's Style section (05-card-window.md), and as a **popover** opened by Style… from a card/lane context menu or the menu bar (Board ▸ Style…, ⌥⌘S — 11-command-nexus.md; selection-aware: it styles the selected cards or lane, and with nothing selected, the board). One component, one behavior — replacing the pathfinder's swatch-row-plus-Style-popover split, whose functions were right and whose form wasn't. **The anchors compose the halves they need** (2026-08-06): the card sidebar shows the symbol grid with the **color combo** (below) standing in for the background half — the narrow context the combo was built for; the Style… popover carries both grids in full. (The board popover was briefly a third anchor — the background half embedded in its Theme tab — until the 2026-08-07 Theme rework made that tab preset-only; Style… with nothing selected is the board's manual grid now, and the popover's symbol picker beside the rename field still owns the board glyph.)
+One **style editor** component — a background palette grid and a curated symbol grid — presented as a **popover** opened by Style… from a card/lane context menu or the menu bar (Board ▸ Style…, ⌥⌘S — 11-command-nexus.md; selection-aware: it styles the selected cards or lane, and with nothing selected, the board). One component, one behavior — replacing the pathfinder's swatch-row-plus-Style-popover split, whose functions were right and whose form wasn't. **The card window sidebar now styles through the compact `SymbolPicker` instead of this component** (2026-08-06 anchor-ownership rule for the background half; the symbol half followed the same way on 2026-08-08): the sidebar pairs the **color combo** (below) — standing in for the background half, the narrow context the combo was built for — with the picker's own well and popover-hosted `CuratedSymbols` grid, so this component now has exactly one anchor left, the Style… popover, which alone carries both grids in full. (The board popover was briefly a third anchor — the background half embedded in its Theme tab — until the 2026-08-07 Theme rework made that tab preset-only; Style… with nothing selected is the board's manual grid now, and the popover's symbol picker beside the rename field still owns the board glyph — the same `SymbolPicker` the card sidebar now uses.)
 
 - **Curated-first, panel-backed** (re-ratified 2026-08-06, reversing 2026-07-29's palette-only ruling): the background grid offers the 12 palette colors — every one AA-verified through one code path (ratified 2026-07-29: palette names route through the same runtime ink-selection seam as hand-written hex — the appearance flip picks the readable label vocabulary — and PaletteContrastTests pins that the chosen ink meets AA in both appearances for all 12 backgrounds, so palette drift can never silently break it) — plus a leading **None** well that removes the `background` key. Beside the grid the vocabulary now has a second, compact form: the **color combo** — a swatch-faced popup listing None, the role's twelve, the current off-palette value verbatim when there is one, and **Other…**, which opens the system Colors panel. The panel is the in-app escape hatch the 2026-07-29 ruling withheld: a pick landing exactly on a palette color stores the *name* (so a re-pick never drifts to a hex spelling), anything else stores the hex — the same unlimited vocabulary hand-editing always had, now pickable. An arbitrary pick changes no contrast story (it lands on the identical runtime ink computation hand-written hex already gets — 10-accessibility.md), and the quick-style recents stay palette-vocabulary: a panel pick never enters them.
 - **Curated symbol grid**: a hand-picked set (roughly five dozen kanban-relevant SF Symbols); its leading well is the level's default symbol and removes the `icon` key. Any other SF Symbol name works written by hand — named symbols the running OS knows, that is: inventories grow per macOS release, so a newer-OS name renders the level default on an older Mac, value preserved on disk — the palette stance again. No full-browser escape hatch in-app; the raw file is the escape hatch. (Symbols keep this stance deliberately — the 2026-08-06 color-panel reversal above is colors only: the system offers a Colors panel worth deferring to, and no symbol browser of equal standing.)

DESIGN/05-card-window.md

@@ -63,7 +63,7 @@ Stacked sections under small-caps headers, in this order; quiet rows, read-optim
 
 ### Style
 
-The card-level styling home: the **Background color combo** over the **curated symbol grid** (03-board-ui.md ▸ Styling ▸ Controls, its 2026-08-06 anchor-ownership rule) — the sidebar is exactly the narrow context the combo was built for, so it stands in for the well grid's background half here, panel escape hatch included; the full grid remains the surface at the other anchors. Card styling is discoverable here without a context menu; the component family is shared with the board popover and Style….
+The card-level styling home: the **Background color combo** over the compact **`SymbolPicker`** (03-board-ui.md ▸ Styling ▸ Controls, its 2026-08-06 anchor-ownership rule for the background half, extended to the symbol half on 2026-08-08) — the sidebar is exactly the narrow context the combo was built for, so it stands in for the style editor's background half here, panel escape hatch included, while the picker's own well and popover-hosted grid — fed `CuratedSymbols`, not the picker's smaller general-purpose default, so a card's curated vocabulary doesn't shrink — stands in for the symbol half the same way; the full style editor's grid remains the surface only at Style…. Card styling is discoverable here without a context menu; the picker is the same reusable control the board popover's glyph picker beside the rename field uses.
 
 ### Details — unknown frontmatter keys