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/components/pilot/sections/WhatWeKnow.tsx

@@ -11,6 +11,7 @@
  * and renders the section. Loading/refresh logic lives in the parent
  * (AssistantChatPage) so it can coordinate with the chat send cycle.
  */
+import { Loader2 } from 'lucide-react'
 import { cn } from '@/lib/utils'
 import type { SessionFact } from '@/api/sessionFacts'
 import { WhatWeKnowItem } from './WhatWeKnowItem'
@@ -48,9 +49,25 @@ export function WhatWeKnow({
           What we know
           <span className="text-muted-foreground">·</span>
           <span className="tabular-nums">{count}</span>
+          {loading && (
+            <span
+              className="ml-auto flex items-center gap-1 text-[0.625rem] font-medium normal-case tracking-normal text-muted-foreground"
+              title="AI may be synthesizing new facts from this turn"
+            >
+              <Loader2 size={10} className="animate-spin" />
+              synthesizing
+            </span>
+          )}
         </div>
       </div>
 
+      {count === 0 && loading && (
+        <div className="space-y-2 px-1 py-2">
+          <div className="h-3 w-3/4 rounded bg-elevated/60 animate-pulse" />
+          <div className="h-3 w-1/2 rounded bg-elevated/60 animate-pulse" />
+        </div>
+      )}
+
       {count === 0 && !loading && (
         <div className="text-[0.75rem] text-muted-foreground italic px-1 py-2">
           Nothing confirmed yet — facts appear here as the engineer answers questions and runs checks.