feat(pilot): Phase 7 — polish (loading/empty states, shortcuts, responsive drawer)

- WhatWeKnow shows a "synthesizing" indicator + skeleton pulse while the
  chat cycle is in-flight; task-lane header mirrors the signal with a
  "thinking" pip so engineers know the AI is still working.
- Quiet-state hint when the lane is open (facts exist) but no open
  questions, checks, or active fix — keeps the surface from looking
  "finished" when the AI is about to follow up.
- Keyboard shortcuts: ⌘↵/Ctrl+↵ send in the composer (plain Enter still
  sends), ⌘G toggles the Script Generator panel for the active fix,
  `?` opens a new ShortcutsHelpOverlay listing all bindings. ⌘K palette
  was already wired in TopBar.
- Responsive: below 1200px the task lane collapses to a bottom drawer
  with a backdrop + a floating "Tasks ●" toggle button. TaskLane now
  takes a `variant: 'side' | 'drawer'` prop; drawer variant drops the
  resize handle and uses the shared slide-in-bottom animation.
- Build hygiene: fixed a pre-existing TS error in confirm-post error
  handling (duplicate `response` type keys) and an unused-import warning
  in TemplatizePrompt.

Verified: `npx tsc -b` and `npm run build` both clean against the dev
stack; Vite HMR applied each change without errors.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/hooks/useMediaQuery.ts

@@ -0,0 +1,27 @@
+import { useEffect, useState } from 'react'
+
+/**
+ * SSR-safe CSS media-query hook. Returns the current match boolean and
+ * re-renders on viewport changes. Used by /pilot to swap the task lane
+ * between side panel (≥1200px) and bottom drawer (<1200px) per Phase 7.
+ */
+export function useMediaQuery(query: string): boolean {
+  const [matches, setMatches] = useState<boolean>(() => {
+    if (typeof window === 'undefined') return false
+    return window.matchMedia(query).matches
+  })
+
+  useEffect(() => {
+    if (typeof window === 'undefined') return
+    const mql = window.matchMedia(query)
+    const handler = (e: MediaQueryListEvent) => setMatches(e.matches)
+    // Sync once on mount in case state drifted between render and effect.
+    setMatches(mql.matches)
+    mql.addEventListener('change', handler)
+    return () => mql.removeEventListener('change', handler)
+  }, [query])
+
+  return matches
+}
+
+export default useMediaQuery