feat(tui): render hierarchical agent tree path (root/agent/sub-agent) instead of raw thread UUIDs (#23588)

[andrei-hasna]

What

The Codewith TUI never rendered the canonical AgentPath (/root/agent/sub_agent) the fork already composes server-side. Collab transcript rows fell back to the raw 36-character thread UUID whenever an agent had no nickname, e.g. Waiting for 019f8894-89dc-70f2-ad8e-d74deba8ed9b.

Addresses upstream openai/codex#23588.

The single choke point

multi_agents.rs::agent_label_spans() feeds all seven collab rows (Waiting for / Spawned / Sent input to / Resuming / Resumed / Closed / wait-complete). The no-nickname branch printed thread_id.to_string() (full UUID). It now renders a precomputed hierarchical tree_path, and as a last resort an 8-character short id — never a full UUID.

How

• AgentMetadata / AgentLabel gain a tree_path; the no-nickname branch prefers it, then a short id.
• AgentNavigationState gains parents and paths maps so ancestry survives thread switches (which rebuild the ChatWidget).
• New App::agent_tree_path resolves in order:
  1. the server-composed authoritative AgentPath (leading / stripped, leaf swapped for the thread's nickname when known);
  2. else a parent-chain walk to root, labeling each node by nickname → [role] → 8-char short id, with a visited-set cycle guard and an …/ prefix when the chain to root cannot be confirmed;
  3. else thread_label (short id, never a full UUID).
• parent_thread_id + source.get_agent_path() are captured at the ThreadStarted, thread/read liveness, loaded-subagent backfill, and local/external spawn upsert sites.

Edge cases handled

• Depth cap (4 segments): root/…/<parent>/<leaf>, with per-segment grapheme truncation (truncate_text).
• Cycle / self-parent: visited-set guard terminates; result is …/-prefixed.
• Orphaned parent (edge → uncached thread): terminates; result is …/<leaf>.
• Non-sub-agent threads (/side forks, primary): no agent_path, no parent → thread_label, unchanged.
• A full UUID is never emitted anywhere.

Tests

• agent_tree_path unit tests (thread_routing.rs): authoritative-path formatting + nickname leaf swap; parent-walk nickname→role→short-id; depth-cap collapse; cycle guard; orphaned parent; primary → thread_label; unknown thread → short id. Each asserts the output never contains a 36-char UUID.
• multi_agents.rs rendering tests: no-nickname row renders the tree path (and, without one, an 8-char short id) instead of the receiver UUID.
• Existing collab_agent_transcript / collab_resume_interrupted snapshots are unchanged (they use nicknames → first branch).

Second raw-UUID surface fixed

The live "Waiting for N agents" status indicator (collab_wait_status.rs) also rendered the raw thread UUID for nickname-less agents. It now uses the same nickname → tree_path → 8-char short id fallback.

Verification (Blacksmith, codex-tui)

3447 tests run: 3447 passed, 4 skipped (exit 0)

New tests, all passing:

• agent_tree_path_* (8): authoritative-path + nickname leaf swap, without-nickname, parent-walk nickname→role→short-id, deep-path collapse, cycle guard, orphaned parent, primary→thread_label, unknown→short id (each asserts no 36-char UUID in output).
• multi_agents::nickname_less_row_renders_tree_path_instead_of_uuid and ..._renders_short_id_not_uuid.
• loaded_threads::captures_authoritative_agent_path_and_parent_for_loaded_subagent.

Two snapshots updated — both flip a full UUID to an 8-char short id (the intended fix, reviewed):

• app_server_collab_spawn_completed_renders_requested_model_and_effort: Spawned 019cff70-…-b91781b41a8e → Spawned 019cff70.
• collab_wait_status::multiple_wait_status: • 019cff70-…-b96db334332d — Working → • 019cff70 — Working.

TUI-only rendering change; does NOT modify server-side path composition.