fix(tui): stop stale cached session title from pinning New Session

[SparkofSpike]

Summary

Session titles were stuck at "New Session" forever: after the first user message, the title computed from the conversation was overwritten by a stale copy held in the in-memory session metadata cache, and the cache itself is only refreshed at the end of each snapshot. A snapshot taken before the first user message pinned the placeholder, and every later snapshot restored it.

Changes

• fix(tui): stop stale cached session title from pinning "New Session" (tui/ui/frame.rs): build_session_snapshot no longer restores the title from the cache unconditionally. Title now resolves in priority order: (1) the persisted disk record when the session already exists (a user rename applied through the session manager survives autosave — feat: sidebar sessions panel with auto-resume and session history browsing #2934 / v0.9.2 Control plane: multi-session dashboard with peek approvals #4397 behavior preserved); (2) the in-memory cache when no disk record exists for the session yet (sessions that have never been saved); (3) the title computed from the conversation (first user message). A placeholder that survived from an earlier snapshot yields to the computed title once a user message exists, healing both fresh and pre-existing sessions.
• refactor(tui): centralize the placeholder title string (session_manager.rs, session.rs, session_resume.rs): the "New Session" placeholder is now the DEFAULT_SESSION_TITLE constant (5 usages replaced), so the healing rule in build_session_snapshot cannot drift from the generator.
• test(tui): regression coverage (tui/ui/tests.rs): two new tests — a stale cached placeholder no longer overrides the generated title, and a persisted placeholder record yields to the computed title once the conversation has content. Both fail on the old code.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Tests

Testing

• cargo test -p codewhale-tui stale_cached_placeholder_title — 1 passed
• cargo test -p codewhale-tui persisted_placeholder_title — 1 passed
• cargo test -p codewhale-tui picker_rename — 2 passed (rename survives autosave regression)
• cargo test -p codewhale-tui full suite — 9708 passed; 10 failures verified unrelated: 6 pre-existing on main (verified via stash), 4 parallel-flaky (pass in isolation)
• Manual testing: built codewhale-tui (debug), sent a first user message in a new session — title updated from "New Session" to the message content; renamed sessions keep their title across autosave

Checklist

• Updated docs or comments as needed
• Added or updated tests where relevant (2 regression tests)
• Verified TUI behavior manually if UI changes
• Harvested/co-authored credit uses a GitHub numeric noreply address

Related Issues

No-Issue: session title stuck at "New Session" after sending messages was found by myself, no relevant issues.

[SparkofSpike]

Well, the commits on main are landing way too fast for me to keep up, so I'll just leave this PR here as is.

Hi @Hmbown, when you're up, could you take a look and merge this manually? Maybe the CodeWhale Bot should create its own branch and batch several commits together before submitting — that would make this a lot easier to catch up with.

[Hmbown]

Well, the commits on main are landing way too fast for me to keep up, so I'll just leave this PR here as is.

Hi @Hmbown, when you're up, could you take a look and merge this manually? Maybe the CodeWhale Bot should create its own branch and batch several commits together before submitting — that would make this a lot easier to catch up with.

That's a great idea - sorry - I've been trying to get this new release out and keep running into things I want to fix. I'm able to get this merged - don't worry! Thank you so much for this!!

I've just added a billion issues for 0.9.5 if you want to see where things are headed 🙂

[SparkofSpike]

No worries at all — shipping a release is way more important than keeping up with it. Thanks for merging it manually, really appreciate it!