Feature proposal: hierarchy tree for Agent Orgs in the sidebar #283

We have been dogfooding Agent Orgs with many members/sessions and found that the current flat sidebar becomes hard to reason about once an org starts spawning workers, sessions, and worktrees.

A useful UI pattern from our fork is an explicit hierarchy tree in the workstation sidebar:

Organization
  ├─ Agent / Member
  │   ├─ Session
  │   │   └─ Sub-session / Worktree / worker run

What it gives operators:

• Parent/child visibility: which session belongs to which org/member.
• Relationship visibility: spawned worker sessions and worktrees remain attached to their origin instead of becoming anonymous flat rows.
• Level badges: rows can show whether they are org / member / session / worker/worktree.
• Actions in context: session row actions (more/actions/context menu) stay available inside the hierarchy, not just in the old flat list.
• Better debugging for orchestration: when a planner creates work for implementers/reviewers/testers, the tree makes it obvious where execution moved.

This fits especially well with the recent Agent Org work around eligible_member_ids, task ownership, and CLI launch configuration: those features improve the runtime model, but operators still need a spatial view of the hierarchy and associations.

Implementation notes from our fork, if useful:

• 9dd5f664 — feat: add org2 hierarchy tree
• 4c3e5ff5 — add level badges
• 6e42d5e6 — enable org tree session actions
• ab0a2575 / dabbb8ab — keep session row actions / more menu visible inside tree rows

The main files touched were around:

• src/scaffold/NavigationSidebar/connectors/WorkstationSidebarConnector/index.tsx
• src/scaffold/NavigationSidebar/connectors/WorkstationSidebarConnector/org2Tree.test.ts
• src/scaffold/NavigationSidebar/connectors/useWorkstationSidebarContextMenu.ts
• src/scaffold/NavigationSidebar/connectors/WorkstationSidebarConnector/sessionRowActions.tsx

We can split this into a focused PR if the direction matches the product roadmap.