tool timeline in sidebar + compact chat tools + scroll fixes

- SessionDigest now includes live tool timeline, plan steps, knowledge
- ToolCallGroup compact: single-line with collapsible names only (no JSON)
- Activity bar moved to bottom of messages, smart scroll respects user position
- setGoal now sets status=executing (removed stuck planning state)
- PlanProgress merged into SessionDigest, removed from TaskContextPanel
- New toolTimeline derived store in chat.ts

cmd/nomos/store.go

@@ -358,13 +358,16 @@ func (s *store) taskEntityPtr(ctx context.Context, sessionID string) *uuid.UUID
 	return &id
 }
 
-// setGoal records the task's goal and moves it into planning. Emits goal.set.
+// setGoal records the task's goal and moves it into executing. The `planning`
+// intermediate state was removed (2026-07-14) — it was indistinguishable from
+// `active` to the operator and caused sessions to appear stuck when the agent
+// called set_goal but never propose_plan (observed in production).
 func (s *store) setGoal(ctx context.Context, sessionID, goal string) error {
 	if s == nil || sessionID == "" || sessionID == "ephemeral" {
 		return nil
 	}
 	if _, err := s.pool.Exec(ctx,
-		`UPDATE agent_sessions SET goal = $2, status = 'planning', last_active_at = now() WHERE id = $1`,
+		`UPDATE agent_sessions SET goal = $2, status = 'executing', last_active_at = now() WHERE id = $1`,
 		sessionID, goal); err != nil {
 		return err
 	}