feat(session): show the live session name in the Status tab

[ayush5harma]

Summary

This is the foundation for showing the session name. It gets the name into the app through the SDK's public session API and shows it in the Status tab. Where else to show it is left for you to decide (see Notes).

• Source of the title. The bridge reads the title only through getSessionInfo(sessionId, { dir }).customTitle and sends a new session_title_update session update. The type is added in agent-sdk/src/types.ts and src/agent/types.rs together.
• When it reads. After a connect, a session replacement, a conversation_reset and every top-level turn result. Also after the Status tab's existing rename_session and generate_session_title succeed; both keep using renameSession() and the SDK's title generation as on main. A read that a later read overtakes is dropped, and no other bridge state is kept.
• Rust.
  • session_runtime.session_title is the one copy of the title. It is cleared with the session identity and on a conversation reset, as SDKConversationResetMessage asks. A repeated title is stored idempotently.
  • Control characters, C1 and DEL included, are stripped once in the converter.
• UI. The Status tab shows the name. Its rename draft (r) and title generation (g) start from it, so both use the live name instead of the session list's snapshot.
• Docs. A Session Name section in commands.md, and a session-title owner table in architecture.md, which separates the live title from the session list's snapshot.

Why

On main, a /rename typed in the composer, or a name given at launch, never reaches the Status tab. The tab shows the session list's snapshot, which nothing refreshes after a typed rename. This is the session-name half of #438; the reply half is #444.

#442 tried this with undeclared stream fields, raw transcript records and --name. This version uses only the session API, following your review on #443.

Refs #438

Validation

• Automated, on this branch (macOS 27.2, Apple Silicon, rustc 1.98.1 from nixpkgs rather than the CI toolchain):

  • cargo fmt --all -- --check, cargo fetch --locked: pass

  • cargo clippy --locked --all-targets --all-features -- -D warnings: pass, with the same five clippy 1.98 lints allowed that main fails (collapsible_match, manual_is_multiple_of, manual_is_variant_and, map_unwrap_or, while_let_loop)

  • cargo test --locked --all-features: pass. The serial terminal_resize run: pass.

  • agent-sdk: npm run build, test, lint, knip and audit: pass. quality:duplicates finds no clone in a file this PR touches.

  • The bridge test spawns the bridge with a stubbed SDK (getSessionInfo, renameSession, query). It asserts the NDJSON for:

    • resume;
    • a title that appears after the first turn;
    • /rename;
    • a /clear replacement;
    • a conversation reset;
    • a Status-tab rename and title generation;
    • a dropped stale read;
    • a failing read.

    Removing the stale-read guard makes the test fail.

  • The Rust tests cover the converter and reset handling. A PTY test renames through the fake bridge and reads the Status row.

• Manual: I drove the debug binary in tmux against the Claude Code bundled with the pinned SDK (2.1.288). After /rename status-probe-title3, then /config and Tab to Status, the tab read Session name: status-probe-title3. Nothing refreshed the session list after that typed rename, so the value came from the live title.
• Screenshot/video (if UI changed): the screen text above. The Status tab's existing name row now shows the live title.

Notes

• Breaking changes: N/A
• Docs updated: docs/src/commands.md, docs/src/architecture.md
• No SDK upgrade: everything here is in the pinned @anthropic-ai/claude-agent-sdk 0.3.288. The read points come from behaviour measured on the Claude Code 2.1.288 it bundles: a launch-time name and a /rename reach getSessionInfo only once the turn has finished, and right after init it reports nothing.
• customTitle falls back to a generated title for a session nobody named, although its doc comment describes the /rename title. Such a session therefore shows that generated title after its first turn. No public field tells the two apart, and the docs state this as the API's behaviour.
• Like main, the resume picker's list is not refreshed after a /rename typed in the composer, only on connect, replacement and the Status-tab actions. I left that as it is rather than add state for it.
• Earlier commits on this branch added a composer rule and a tab-title change; the later commits remove both, so the net diff touches neither. If you squash, the PR title describes the result.
• Governance/release impact: N/A

[ayush5harma]

Hi @srothgan, this is ready for review whenever you have time.

Before opening it I read CONTRIBUTING.md, AGENTS.md and docs/src/architecture.md, and applied your feedback from #443 and #441:

• The title comes only from the SDK's public getSessionInfo().customTitle. Nothing reads Claude Code's transcript records, undeclared stream fields or its UI, and the tests stub the SDK rather than write its private file format.
• There is one owner per side: the bridge reads and sends the title, and Rust holds it as a single value. The architecture doc has an owner table for it, separate from the session list's snapshot.
• The wire type changed in types.ts and types.rs together. CHANGELOG is left to you, and there is no agent attribution in the commits.
• There is no SDK upgrade. Everything uses the pinned @anthropic-ai/claude-agent-sdk 0.3.288, and I measured the behaviour on the Claude Code 2.1.288 it bundles.

After a self-review against those rules, I cut this PR down to the foundation:

• The bridge sends the title, and the Status tab shows the live name.
• I dropped the rule above the composer and the tab-title change I had first added, so that nothing imitates Claude Code's interface.
• The net diff is now +522/-27, mostly tests.

One question for you: would you like the session name shown anywhere else, such as the footer or the terminal tab title? I'd rather follow your call on placement than guess. I can do that in a follow-up.

I couldn't apply labels. Per CONTRIBUTING, I think type: feature, area: agent-sdk and area: tui fit.

Could you check it on your end and merge it if it looks good? Happy to change anything you'd like done differently.