story-83: remove active work list from Agents panel

Remove the "agents-at-work" list section from AgentPanel. The roster
badges with flying lozenge animations already convey which agents are
active, making the redundant list unnecessary.

- Remove StatusBadge, DiffCommand, EditorCommand components
- Remove expandedKey, logEndRefs, fade-timer state and effects
- Remove handleStop (no more Stop buttons)
- Keep agents state + SSE subscriptions (roster badges still need it)
- Delete diff-command and fade-out tests (feature removed)
- Add test asserting no agent-entry divs are rendered

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.story_kit/work/2_current/83_story_remove_active_work_list_from_agents_panel.md

@@ -0,0 +1,20 @@
+---
+name: "Remove active work list from Agents panel"
+test_plan: approved
+---
+
+# Story 83: Remove active work list from Agents panel
+
+## User Story
+
+As a user, I want the Agents panel to only show the agent roster (with lozenges) and not a separate list of active work items, since the flying lozenges already indicate which agents are working on which stories.
+
+## Acceptance Criteria
+
+- [ ] The Agents panel no longer displays the list of active work items / agents-at-work section
+- [ ] The agent roster with availability lozenges remains visible and functional
+- [ ] Flying lozenge animations continue to work as before
+
+## Out of Scope
+
+- TBD