PR #1827 - ReviewStage/luke

Summary

Toggle: a sidebar icon button sits just right of the macOS traffic lights, at a fixed position in the drag strip (the button itself is no-drag). It stays in the same spot whether the sidebar is open or folded. Its aria-label is "Hide sidebar" / "Show sidebar", its tooltip adds (⌘B), and it sets aria-keyshortcuts="Meta+B".
Folding: the plans' shell gets a 0 sidebar column, so the work column takes the full width right away. The sidebar slides off the left edge over it, using transform and opacity on --duration-quick / --motion-exit. Those tokens drop to 1ms under reduced motion and to 0 in capture. A folded sidebar is inert, so Tab can't land on rows that aren't visible. While folded, the plan toolbar starts its title clear of the traffic lights and the toggle, and Luke's captions centre on the full window instead of the old work column.
⌘B toggles the sidebar while the Plans tab has the keyboard. It does nothing in Settings, under a sheet, or behind the sign-in gate. The Keyboard shortcuts page lists it as a fixed row, and Settings search can find it.
Persistence: the folded state is kept in the renderer's localStorage. That lives under Luke's state root, so it survives a relaunch. No other window or process reads it, so it does not go through the settings file as a schema setting. A fixture run starts with the sidebar open and stores nothing, so evidence frames never pick up a developer's own folded state. This matches the side panel from #1829.
Settings: Settings always shows its page list and never shows the toggle. Leaving Settings brings back the plans view folded or open, as it was.

One departure from the brief: the brief asked for a width/opacity transition. design/check-design-contract.mjs (run by check.sh) and docs/DESIGN.md refuse layout-property transitions because text reflows on every frame. So the column changes size instantly and the sidebar moves with transform and opacity only.

The settings-panel props builder moved to #testing/settings-panel-props. It now has two callers: the existing settings-panel test and the new shell test.

Evidence

Platform-independent checks: ./scripts/check.sh exit 0 (Linux).
New desktop/desktop-shell.test.ts (jsdom) goes through DesktopShell and useSidebarCollapse. It covers four things:
- The toggle hides and restores the sidebar.
- The folded state survives a remount.
- ⌘B folds and unfolds the sidebar on Plans.
- Settings keeps its page list, shows no toggle, ignores ⌘B, and hands the plans back still folded.
- A fixture run starts open and doesn't touch the stored state. Control-B is left to text fields.
macOS Electron verification (./scripts/verify.sh): not run. CI could not verify this change: it builds nothing for the Mac, and this PR was written in a Linux sandbox. LUKE-159 is the manual Mac pass.

Visual evidence

Fixture screenshots: not attached. I rendered DesktopShell over the built styles.css in headless Chrome on Linux and checked four states: expanded, folded, Settings while folded, and the Keyboard shortcuts row. Chrome draws no traffic lights, and the toggle's 80px left offset assumes they end at about 72px, so its position next to the real lights is unverified on a Mac.

Physical-device evidence

Screenshot or screen recording: not attached
Device/display configuration: not recorded

Invariants

./scripts/check.sh green. ./scripts/verify.sh not run (no Mac available).
JSON Schema goldens unchanged.
The behavior change ships with a test that fails without it. No change-detector test added.
Gateway envelope goldens unchanged.
No new as type assertion.
No new Effect.runPromise/runSync/runFork.
No new raw async primitives.
No discarded Effect.
Test count grows by three. The shortcuts search expectation now includes the new row.
No hand-rolled file replaced.
CLAUDE.md/AGENTS.md untouched.
PRIVACY.md unchanged. The stored value is one boolean and leaves the machine nowhere.
No dependency changes.

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