feat(sessions): opt-in renaming of sessions after their pull requests

[ghackett]

Summary

Adds a "Rename sessions after their pull requests" switch (default off) to the Session list preferences group. When on, a session is retitled to match the newest pull request detected in it, so the sidebar reads as a list of the PRs being worked on.

• Every detection path is covered: an open tab's PR poll (MainWindow._on_tab_prs_changed), the sidebar row's PR-menu refresh for sessions with no open tab (SessionRow._pr_menu_refreshed), and a one-time sweep over all saved PR lists when the setting is switched on (SessionStore.apply_pr_titles from _apply_preferences) — so existing sessions with saved PRs retitle immediately.
• Manual renames always win: the PR title lands in the generated-name slot (like auto-titling), so display_name's precedence keeps an explicit rename on top, and the auto-title paths already know to skip a session that has a generated name.
• Waits for a real title: a fresh pr-link transcript record carries no title until a gh reply enriches it; the new prstatus.newest_title helper skips untitled records, so nothing is renamed until the title is actually known (and a titled predecessor is never blanked by a newer bare link).
• Multiple PRs: saved lists are oldest-first, so the newest titled PR — the one being worked on now — is what the session is named after. If the PR's title later changes on GitHub, the next refresh that lands it renames the session to match.
• No churn: a rename only happens when the newest title differs from the current generated name, so the 1s tab poll doesn't rewrite state.json on every tick.

The core logic lives in GTK-free modules (prstatus.newest_title, SessionStore.apply_pr_title), with tests in test_prstatus.py, test_store.py, and test_state.py.

Screenshots

The new switch in Preferences → Session list:

A session renamed to its PR's title in the sidebar:

🤖 Generated with Claude Code

https://claude.ai/code/session_01REtnD8HVyX4PBz1cNYDpmk

[ghackett]

@claude review

[claude]

Claude finished @ghackett's task in 2m 50s —— View job

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Claude finished reviewing

• Gather context (read diff, CLAUDE.md)
• Review core logic (prstatus.py, store.py)
• Review UI/wiring (prefs.py, sidebar.py, window.py, state.py)
• Review tests
• Post final review

Summary

This is a clean, well-scoped feature. I traced all three write paths (_on_tab_prs_changed, _pr_menu_refreshed, apply_pr_titles sweep on preferences apply) and the precedence chain (display_name → get_name → get_generated_name → preview → id prefix). Everything lines up with the PR description:

• newest_title correctly relies on the documented invariant that saved PR lists are oldest-first (confirmed via prstatus.py's "chronological" comment and merge_ordered's tests), and skips untitled records so a titled predecessor is never blanked by a fresh bare pr-link.
• Writing to the generated-name slot (not names) is the right call — it reuses the existing "manual rename wins" precedence and the existing auto-title skip-if-generated-name-set guards, without needing new state or new skip logic.
• The no-churn guard (title == get_generated_name(...)) correctly prevents the 1s tab poll from rewriting state.json every tick.
• set_generated_names batches to one save() call, matching apply_pr_titles' one-sweep intent.
• GPL modification-notice headers are correctly updated on every pre-existing file touched (prefs.py, sidebar.py, state.py, store.py, window.py); prstatus.py's newest_title addition needs no notice since the file postdates the fork.
• po/collins.pot strings match the two new user-facing strings in prefs.py.
• Tests are thorough: test_prstatus.py covers the ordering/skip/none cases for newest_title, test_store.py covers off-by-default, the win-over-manual-rename case, waiting for a title, and the preferences-toggle sweep (including a second session that's correctly left alone because it has no title yet), and test_state.py covers the new setting's persistence/default.

Minor observations (non-blocking)

• store.py:454-474 — apply_pr_titles() is called unconditionally from _apply_preferences() on every preferences save, not just when pr_title_sessions is toggled (e.g. also fires when the user just changes font size). It's guarded by the setting check and the diff-before-write check, so it's a no-op walk over self.sessions rather than actual churn — fine given the size of that dict, just noting it's broader than strictly necessary.
• collins/prstatus.py:428-436 — newest_title's docstring nicely documents the oldest-first assumption, but nothing in newest_title itself asserts/enforces it; it's an implicit contract with whatever writes the saved list (to_records/merge_ordered). Not a bug — just worth keeping in mind if a future change ever reorders that list.

I was unable to execute python3 -m pytest in this sandbox (the command requires approval that isn't available in this run) — you may want to add python3/pytest to --allowedTools so a future review can actually execute the suite rather than just reading it. I did not find anything in the code or tests that suggests they'd fail.

No bugs found; nothing here I'd block on.
(branch)

[ghackett]

Addressed the review's two observations in a8638dc:

• Sweep on every preferences save — apply_pr_titles now detects the off→on flip itself (the store remembers the last-seen setting value), so a save that didn't just enable the setting returns without walking the sessions. A new test (test_apply_pr_titles_sweeps_only_on_the_off_to_on_flip) pins the semantics, including that a list saved behind the sweep's back is left to the per-detection hooks until a fresh flip.
• newest_title's oldest-first assumption — left as documentation: the docstring names the invariant, and its writers (to_records over merge_ordered output) are covered by test_records_roundtrip_in_order and the merge-order tests, so a future reordering would surface there.