feat: org chart sidebar section + pane with agent management

[aterrylu]

Summary

• Org Chart as sidebar section: Replaced the AGENTS/ORG CHART tab bar with clickable section headers. "ORG CHART" opens the card-based hierarchy panel as a pane on the right (same as clicking a session opens its terminal).
• New pane type: Added "orgchart" to ActivePane union, renders in SessionMountLayer, shows in tab bar — integrates fully with the existing split-pane/tab system.
• Stopped agent management: Toggle to show/hide stopped agents (eye icon in AGENTS header). Remove with confirmation in both sidebar (inline confirm) and org chart cards (overlay with trash icon).

Key design decisions

• Org chart is a singleton pane (fixed ID "orgchart") — only one can exist, openOrgChart uses findLeafByPaneId to switch to existing tab instead of creating duplicates
• Exited sessions stored separately from live sessions to avoid broken terminal WebSocket reconnect loops
• removeSession throws on failure (not silent swallow) — callers keep confirmation UI open so user knows it failed
• UI labels say "stopped" consistently (not "exited")

Files changed

File	Change
store.ts	ActivePane type, openOrgChart/removeSession/toggleShowExitedAgents actions, exitedSessions state
Sidebar.tsx	Remove tab bar, add section headers, stopped agent toggle + remove
HierarchyPanel.tsx	Remove panel header, add trash overlay + confirm on cards, include exited sessions in status map
SessionMountLayer.tsx	Render HierarchyPanel in pane slot
TabBar.tsx	Handle orgchart tab title
Codicon.tsx	Add eye, eye-closed, trash icons

Test plan

• make check passes (lint + types + 63 tests)
• Click "ORG CHART" → opens hierarchy panel as pane on right
• Click session → switches away; click "ORG CHART" → switches back
• Tab bar shows "Org Chart" with close button
• Eye icon toggles stopped agents in sidebar
• Trash icon on stopped agent → "remove" / "cancel" confirmation
• Org chart card hover → trash overlay → confirm → removes agent
• Removing running agent kills first, then permanently deletes

🤖 Generated with Claude Code

[nox-0x]

🟡 Warning

Problem: In AgentCard's handleRemove, the isRunning variable is captured at component render time. If killSession succeeds and the store's polling cycle updates session.status to 'exited' before removeSession completes, the component re-renders with isRunning = false. This can cause the confirmation overlay to visually disappear while removeSession is still in-flight — confusing UX.

Why it matters: The user may see the confirm overlay vanish or the agent appear as stopped mid-operation.

Suggested fix: Re-check session status inside handleRemove rather than relying on the render-time const:

[nox-0x]

Suggested fix: Capture running status at click time instead of render time:

[nox-0x]

🟡 Silent error feedback in exited-agent removal

Problem: In Sidebar.tsx, when removeSession(s.id) fails, the catch block silently swallows the error — confirmRemoveId stays set (keeping dialog visible) but the user gets no error message. If the backend returns a non-OK status (e.g. 404 session already gone, 500 server error), the user sees no indication what went wrong.

Why it matters: The confirm dialog staying open is a decent signal something went wrong, but without a visible error message the user may click Remove repeatedly or assume the UI is broken.

Suggested fix:

onClick={async () => {
  try {
    await removeSession(s.id);
    setConfirmRemoveId(null);
  } catch {
    // Keep confirm visible + surface a transient error message
    // e.g. setErrorId(s.id) to show "Failed to remove agent" inline
  }
}}

Alternative (minimal): At minimum, log to console with the session ID so it's debuggable: console.error('[Sidebar] removeSession failed for', s.id).

[nox-0x]

Overall solid implementation. The org chart as a pane, exited session separation, and singleton pane pattern are all well-designed. Two non-blocking UX issues flagged in comments: (1) isRunning captured at render time in handleRemove creating a potential mid-operation visual inconsistency, (2) silent error swallowing in Sidebar removeSession without user-visible feedback. Both are minor — fix before merge or track as follow-up.