feat(web): show where each subagent works in the Agents panel

[adampeterhiggins]

The Agents panel didn't say where a subagent was working. You couldn't tell whether an agent was editing the thread's own worktree or a worktree of its own.

Each agent now shows its worktree by folder name: in the Agents list row, and as one line in the detail header with the branch and lines changed. Hovering that line shows the full path and branch, each with a copy button. A tag says how we know:

• shared: the provider reported a folder, and it's the thread's own worktree.
• isolated: the provider reported a different folder, for example a Claude agent launched with isolation: "worktree".
• thread folder?: the provider doesn't report where subagents run, so the thread's folder is shown as an assumption.

Before / after

	Before	After
Agents list
Agent detail
Hover

The screenshots use a real Claude thread copied into an isolated worktree database. That thread predates this change, so one task.updated fixture row per agent adds the workspace fields: one shared agent, and one isolated agent with a worktree and line counts.

How

• Contracts: the task linkage gains optional cwd, worktreeBranch, isolation, linesAdded, and linesRemoved, and ingestion persists them. An absent cwd means unknown, not "same as the thread".
• Claude:
  • isolation comes from the Agent tool's launch input.
  • Non-isolated agents get the session cwd, and nested agents inherit their owner's.
  • The Agent tool result's worktreePath, worktreeBranch, and toolStats arrive after the task settles, so the adapter sends them in a status-free task.updated. That's a metadata update and doesn't restart the task or change its liveness.
• Codex: the child thread's thread/started carries thread.cwd, which CodexSessionRuntime used to drop. It now rides on the collab child identity.
• OpenCode: child session.created events carry info.directory, which is now read.
• Cursor, Grok, Antigravity: nothing they send includes a subagent cwd, so the UI falls back to the thread's folder, tagged as an assumption.
• Client: deriveSubagentWorkspace in client-runtime compares the agent's cwd with the thread's worktree (or project root).
• Web: AgentWorkspace.tsx renders the header line with its hover card and the row chip.
• Surfaces: mobile doesn't render subagents, so this is web and desktop only. No new events or websocket traffic; the fields ride on existing task events.
• Docs: updated docs/fork-differences.md and docs/user/thread-sidebar.md.

Verification

• Focused tests pass for the new behavior: the client fold and workspace derivation, the Claude adapter (shared, isolated with a reported worktree, remote), the Codex runtime and adapter carrying thread.cwd, and the OpenCode child directory.
• Web, server, client-runtime, and contracts typecheck clean. Targeted lint shows no errors; the only warnings are ones ChatView.tsx already had.
• ThreadSettlementReactor.test.ts storage-cleanup tests fail locally in this ~/.t3 worktree. They don't touch any code changed here.

Model: Claude Opus 5.5. Harness: Claude Code through T3 Code.

🤖 Generated with Claude Code