Add an expand / collapse (maximize) toggle to the chat composer

[DragonnZhang]

Closes #48

What & why

OpenWork's chat composer (FreeFormInput) auto-grows as you type, but only up to
a fixed cap — min(66% of window height, 540px). There was no way to
deliberately give the input a large editing area, so drafting or editing a long
prompt meant writing and scrolling inside a small box even with a tall window.

Comparable desktop chat surfaces (Claude's desktop app, ChatGPT desktop, Codex
desktop) all offer a maximize / expand affordance on the composer. OpenWork's
toolbar already has a model picker, a thinking-level picker, a context-usage
indicator and an attach control, but no expand toggle — this adds one.

This adds a small expand / collapse toggle to the composer's right-side
controls, next to the thinking-level and model pickers and following the same
!compactMode rule:

• A Maximize2 icon when collapsed / Minimize2 when expanded, with a tooltip
  ("Expand composer" / "Collapse composer") and aria-pressed reflecting state.
• Clicking it maximizes the input to max(78% of window height, 560px) — applied
  as both minHeight and maxHeight on the editable area so the box is genuinely
  large even when empty — recomputed on window resize alongside the existing cap.
• Clicking again collapses back to the normal auto-grow cap.
• The maximized state resets on session switch, so a new conversation starts
  compact.

Frontend-only. It only toggles renderer layout state (isComposerExpanded)
and the inline height style already applied to RichTextInput. No backend /
qwen-code change. Two new i18n keys (chat.expandComposer, chat.collapseComposer)
added to all locales for the tooltip.

Changes

• components/app-shell/input/FreeFormInput.tsx — isComposerExpanded state,
  expandedMaxHeight computed in the existing resize effect, a reset-on-session
  effect, the toolbar toggle button, and the conditional input height.
• packages/shared/src/i18n/locales/*.json — chat.expandComposer /
  chat.collapseComposer in all 7 locales, inserted in sorted position.
• e2e/assertions/composer-expand.assert.ts — new CDP assertion (below).

Verification (DoD)

• bun run typecheck:all — introduces no new errors. Delta vs main is
  zero: the only errors are the 11 pre-existing ones in apps/electron
  (auto-update.ts owner/repo, a settings-default-thinking test tuple, two
  test files importing vitest) — none in the files this PR touches.
• bun test — the set of failing tests is byte-for-byte identical to
  main (verified by diffing the sorted, timing-stripped failure lists from a
  clean-main run and this branch: 56 pre-existing failures, e.g. BrowserCDP,
  BrowserPaneManager, RPC registration profiles, RoutedClient,
  startWebuiHttpServer, resource-bundle, and the i18n sorted checks whose
  first out-of-order key is menu.homepage — far from the chat.* keys added
  here). This change adds zero new failures. (The raw N fail total is
  order-dependent/flaky when the whole suite runs unisolated, which is why the
  repo splits *.isolated.ts; the deterministic signal is the failing-test set,
  which is unchanged.)
• bun run lint:i18n:parity — OK (6 locales, 1544 keys each). The two new
  keys are added to every locale in sorted position.
• Renderer build (bun run electron:build:renderer, where this change lives)
  — ✅ builds cleanly.
• CDP assertion transpiles (bun build e2e/assertions/composer-expand.assert.ts)
  — ✅.

CDP e2e assertion (composer-expand.assert.ts)

Drives the real built app over CDP entirely in the draft (no-session) state — no
seeded conversation needed:

1. The composer renders the expand toggle, initially aria-pressed="false".
2. Measures the input area's height (collapsed).
3. Clicks the toggle → asserts the input height grows to >= 2× the collapsed
   height and the toggle flips to aria-pressed="true".
4. Clicks again → asserts the input height collapses back to roughly its start
   height and the toggle returns to aria-pressed="false".

The height measurements prove the toggle actually resizes the composer, not
merely swaps an icon.

⚠️ Local CDP run was blocked by this sandbox's egress policy, not by the
feature. electron:build:main cannot resolve the libsignal GitHub dependency
(pulled in transitively by the WhatsApp/Baileys worker), and the Electron binary
download 403s from the egress proxy, so the app can't be built or launched here
(xvfb is present; only those network fetches fail). The assertion transpiles
and is included so CI / a reviewer can run bun run e2e in an environment with
normal network access. Everything that doesn't require launching Electron
(typecheck, unit tests, i18n parity, renderer build) passes with zero delta vs
main.

Part of the autonomous desktop-feature loop (loop-bot).

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