workflow: project-driven agent workflow (docs-first, TODO/ROADMAP tracking, verify-before-done)

- system prompt gains a Project workflow block when the repo tracks its own
  progress (TODO.md/ROADMAP.md/docs): read the task list first and keep it
  current, spec-first for non-trivial work, complete unit tests, verify before
  declaring done
- TODO.md + ROADMAP.md loaded as 'Project tracker' instruction blocks, capped
  tighter than AGENTS.md so the agent sees the shape without drowning in it
- one soft nudge per session when a turn writes files without touching the
  task list; suppressed when todo_write was called; never a gate
- /workflow command + panel showing TODO/ROADMAP/docs presence, line/file
  counts, nudge state
- config: workflow.enabled (default true), workflow.docsDir (default docs)
- prompt-cache version key extended with wf: so toggling the workflow busts
  the cached system prompt
- docs: docs/workflow.md, configuration table row, ROADMAP + TODO entries
- tests: test/workflow.test.ts (9 tests)

830 tests pass, typecheck clean, build green, live headless demo verified

src/ui/panel-bodies.ts

@@ -102,3 +102,18 @@ export function changesPanel(session: Session): Panel {
     .join('\n');
   return { title: 'changes', body };
 }
+
+/** Project workflow state: what the repo tracks and how the session behaved. */
+export function workflowPanel(session: Session): Panel {
+  const w = session.workflowStatus();
+  const yes = (b: boolean): string => (b ? 'yes' : 'no');
+  const rows = [
+    ['workflow', w.enabled ? 'on' : 'off'],
+    ['TODO.md', `${yes(w.hasTodo)}${w.hasTodo ? ` (${w.todoLines} lines)` : ''}`],
+    ['ROADMAP.md', `${yes(w.hasRoadmap)}${w.hasRoadmap ? ` (${w.roadmapLines} lines)` : ''}`],
+    ['docs dir', `${yes(w.hasDocs)}${w.hasDocs ? ` (${w.docsFiles} files)` : ''}`],
+    ['reminders sent', w.nudged ? '1 (this session)' : 'none'],
+  ];
+  const body = rows.map(([k, v]) => `${k}: ${v}`).join('\n');
+  return { title: 'workflow', body };
+}