feat(tasks): phase 6 — live TaskContextPanel (goal, plan, question, entities)

Replaces the chat right rail's ad-hoc Digest+Graph stack with a single
TaskContextPanel that renders the task's live working state, driven by the
always-on events stream (not the per-turn chat SSE) so it keeps updating
during server-side auto-continuation/resume:

- GoalHeader: goal + status pill (planning/executing/awaiting_input/done/
  failed), sourced from the sessions list.
- PlanProgress: ordered steps with live status icons + progress bar, hydrated
  via new GET /sessions/{id}/plan; clicking a step with a target opens its
  EntitySheet (no fake "jump to transcript" — bits-ui Collapsible content
  isn't force-mounted, so a DOM-scroll jump would silently no-op for
  collapsed tool groups).
- OperatorQuestion: the pinned structured question card (prompt/why/entity
  chips/option buttons/free-text), hydrated via new GET /sessions/{id}/
  questions; answering POSTs to the existing answer endpoint.
- SessionGraph upgraded to a live entity panel: entity.touched pulses the
  node (animated ring) and shows "Now touching <slug>"; health.changed shows
  a transient diff badge for touched entities.
- SessionDigest gains a success/failure/partial outcome banner and now also
  refetches when the task's status changes, not just on session switch.

Two bugs found and fixed while wiring this up:
- workspace.ts's status-refresh trigger only covered goal.set/task.status;
  question.raised/answered didn't refresh the sessions list, so GoalHeader's
  pill went stale after answering via the panel (resumeSession runs entirely
  server-side — no client 'done' event to piggyback a refresh on). Now every
  status-affecting event triggers the (debounced) refetch.
- Forgot to rebuild the nomos container after adding the /plan and
  /questions endpoints, so they silently fell through to the old default GET
  handler — caught via a live curl diff against the running container,
  not a code read.

Verified end-to-end against the live stack: goal/plan/question all update
without a reload as the agent works; answering a question via the panel
resumes the agent and the header pill correctly flips to Executing;
entity.touched pulses the live graph.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

cmd/nomos/main.go

@@ -255,6 +255,32 @@ func handleSessionDetail(w http.ResponseWriter, r *http.Request, st *store, a *a
 		return
 	}
 
+	// GET /sessions/{id}/plan and /sessions/{id}/questions — REST hydration for
+	// the context panel when it first opens a task; live events carry deltas
+	// from there.
+	if len(parts) == 2 && r.Method == http.MethodGet {
+		switch parts[1] {
+		case "plan":
+			steps, err := st.getPlanSteps(r.Context(), id)
+			if err != nil {
+				http.Error(w, err.Error(), 500)
+				return
+			}
+			w.Header().Set("Content-Type", "application/json")
+			json.NewEncoder(w).Encode(map[string]any{"steps": steps})
+			return
+		case "questions":
+			questions, err := st.getQuestions(r.Context(), id)
+			if err != nil {
+				http.Error(w, err.Error(), 500)
+				return
+			}
+			w.Header().Set("Content-Type", "application/json")
+			json.NewEncoder(w).Encode(map[string]any{"questions": questions})
+			return
+		}
+	}
+
 	switch r.Method {
 	case http.MethodDelete:
 		if err := st.deleteSession(r.Context(), id); err != nil {