feat(ui): native-feeling menus, notices and one vocabulary

[devswha]

Stacked on #179 (base fix/ui-quick-polish); retarget to main once #179 merges.

Summary

Second batch of the native-app design review.

Notices and menus

• Every window.alert (21 in the sidebar controller) → a root Toaster (showToast / showErrorToast): non-blocking, top centre, at most three, errors 8s / notices 4s, held while hovered or focused.
• useAnchoredPopup: the six composer popups (model, preset, permission mode, skills, worktree, workspace target) now share one implementation — portal, anchored above/below and clamped, outside press + Escape close with focus return, arrow-key navigation (none of them had it; the skill picker ignored Escape).
• Context menus: secondary click on a conversation or workspace row opens its full action set at the pointer (useContextMenu) instead of WebKit's "Open Link in New Window" menu.

Permission card

• The whole command is shown, wrapped, instead of one truncated line.
• "Always allow/deny …" are quiet actions on the left; Deny / Allow on the right.
• ⌘↩ / Ctrl+Enter approves the oldest plain request; the plan card's Build finally answers to the ⌘↩ it always displayed. A text field keeps the chord.

Sidebar

• A conversation listed in both Active and its workspace is highlighted only where it was picked; a workspace row is highlighted only when it is itself the selection.
• One vocabulary in all 10 locales: workspace and conversation. "New work item" → "New conversation"; left "Work" → "Active" (no longer collides with the agent panel's Work). Keys that only existed as English fallbacks (archive dialog, add-workspace dialog, primary nav label) are now translated.

Composer and transcript

• Worktree choice is a composer popup, not a bordered native <select>; a running session's location is a tag, not a lookalike button.
• Context gauge is a filled wedge in an outline — it no longer reads as a second spinner beside Stop.
• Scroll-to-bottom sits at the column's trailing edge, off the reading line.
• Work block / tool rows start on the prose edge (measured: chevron 361 → 357 = prose).
• Agent panel shows a conversation worktree as "<repo> worktree" and branch job/<8-char id>, full values in the tooltip.

Cleanup

• Retired dead activeTab / AppTab plumbing and the no-op "Go to Chat" palette action, with their locale keys.
• --success / --favorite tokens replace the last emerald/amber classes (DESIGN.md updated).

Kept on purpose

• Escape while a run is stoppable still stops the run even with a picker open (pinned by ModelAndReasoningPicker.dom "global Stop owns Escape"). Worth revisiting as a product decision: Escape on an open menu currently kills the run.

Verification

• typecheck, lint, check:identity, vite build: pass. test:e2e:gjc 8/8.
• Full suite: server 1449/0, server-bun all 13 files, client 529/0, client-bun all 73 files. scripts 6 failures are the same pre-existing ones as on an untouched checkout (patch appliers / release archive).
• New tests: Toaster.dom, useAnchoredPopup.dom (Escape/focus, arrows, outside press, Stop-owns-Escape), context menu in SidebarSessionItem.menu.dom, SidebarContent.selection.dom, permission shortcut + full command in PermissionRequestsBanner.dom, worktree picker, environment labels, gauge shape.
• Visual QA with puppeteer against a dev server on the dev DB: context menu, permission popup with arrow keys, worktree popup (light), transcript alignment.