The two-homes width rule becomes focused-width parity

Ruled 2026-08-01: the width the user types in is the em-derived figure in
both of ⌘F's homes; the toolbar field's resting width is AppKit's, outside
the invariant — the transient strip never rests, so it has no collapsed
state to mirror. 03 also records the shipped grow-on-focus behavior beside
the default-item sentence.

Claude-Session: https://claude.ai/code/session_01CqjXB7ASoWtbyoGod68k97

DESIGN/03-board-ui.md

@@ -12,7 +12,7 @@ The board window: layout, lanes, cards, and styling. Interaction mechanics (sele
 
 Toolbars are **pure enhancement**: every function they host already has a menu item + shortcut (04-interactions.md's contract), so nothing below is anyone's only path. Both windows' toolbars are **user-customizable, macOS-native** (right-click ▸ Customize Toolbar…, drag to rearrange, system overflow and icon/text display options) — the sets below are shipped defaults, not verdicts. Toolbar item labels match their menu-item titles exactly (Show Trash, Edit Body, Raw Source, …), minus any trailing ellipsis (macOS convention: "Add Attachment…" labels as Add Attachment) — one vocabulary everywhere, and the customize palette self-documents against the menus. One exception: the Undo/Redo toolbar items keep static labels — NSUndoManager rewrites their menu titles dynamically ("Undo Move Card…", 04-interactions.md ▸ Configurable bindings), which a toolbar label doesn't track.
 
-- **Board window default: the search field, nothing else** — trailing, the one default item; the titlebar stays clean. ⌘F always summons search: with the field removed from the toolbar, invoking it surfaces the field transiently until the search clears. **Catalog** (available via Customize): New Card, New Lane, Undo, Redo (the pair disabled only under locks and on empty stacks — re-ruled 2026-07-31, twice: the provider follows the board, so boards without app-managed git — repo-nested included — bind 13-native-undo.md's native stack in **every** tier and Pro git boards bind the git provider — 06-history-undo.md), Show Trash (toggle state matching the View menu checkmark). The board popover deliberately has **no toolbar item** — the window-title widget is its committed home (below), and a second entry would muddy it.
+- **Board window default: the search field, nothing else** — trailing, the one default item; the titlebar stays clean. ⌘F always summons search: with the field removed from the toolbar, invoking it surfaces the field transiently until the search clears. **The field is the platform's own search toolbar item and grows on focus** (2026-08-01): the em-derived width is the *focused* width — applied when the field takes the keyboard, expanding via the item's own animation — and the resting width is AppKit's natural one, not the app's to set. **The two-homes width rule is focused-width parity** (ruled 2026-08-01): the width the user *types in* is the same em-derived figure whichever home the field is in — the toolbar item focused, or the transient strip; the toolbar field's resting width is outside the invariant (the strip never rests — it exists only while a search is live or focused, so it has no collapsed state to mirror). **Catalog** (available via Customize): New Card, New Lane, Undo, Redo (the pair disabled only under locks and on empty stacks — re-ruled 2026-07-31, twice: the provider follows the board, so boards without app-managed git — repo-nested included — bind 13-native-undo.md's native stack in **every** tier and Pro git boards bind the git provider — 06-history-undo.md), Show Trash (toggle state matching the View menu checkmark). The board popover deliberately has **no toolbar item** — the window-title widget is its committed home (below), and a second entry would muddy it.
 - **Card window default: Edit Body · Raw Source · Add Attachment** — the window's three committed functions, all discoverable from its toolbar; the catalog is the same trio. Edit Body is a **single toggle button** (on-state in Edit — mirroring the View ▸ Edit Body checkmark and the ⌘E/Return/Escape grammar; the pathfinder's segmented Preview|Edit is retired). Raw Source is likewise a toggle showing on-state; while source mode is active, Edit Body disables (Cancel/Apply own the exits — 05-card-window.md). Add Attachment stays enabled in every mode — attachment operations never touch `index.md`, so they're safe alongside a raw edit (the sidebar's feedback returns on exit).
 
 ## Lane