feat(sidebar): tooltip with the full title on ellipsised session rows

[ghackett]

What

Hovering a session row in the sidebar whose title is ellipsised now shows the complete title as a tooltip.

How

SessionRow sets has-tooltip and answers query-tooltip itself: the handler checks the name label's Pango layout and only supplies the tooltip while the layout is actually ellipsized, so rows whose titles fit stay tooltip-free. The tooltip lives on the row rather than the label, making the whole row width a hover target — while the per-button tooltips (archive, stop, PRs, …) still take precedence when the pointer is over a button.

Screenshots

The tooltip bubble is composited into the shot (a headless in-process window render can't capture the native tooltip popup), but its content and trigger logic were verified live in the running app: the ellipsised row's query-tooltip handler returned the full title, and a short-titled row declined the tooltip.

🤖 Generated with Claude Code

https://claude.ai/code/session_013k2cKyGZJCk3o9iWoYeou7

[ghackett]

@claude review

[claude]

Claude finished @ghackett's task in 1m 16s —— View job

---

Review complete ✅

• Gather context (PR diff, CLAUDE.md)
• Review collins/sidebar.py changes
• Post review feedback

Summary

Small, well-scoped change. SessionRow now answers query-tooltip itself and only supplies a tooltip when the name label's Pango layout is actually ellipsized (collins/sidebar.py:630-636). Putting the tooltip on the row rather than the label is the right call — it makes the whole row a hover target, and GTK's own per-widget tooltip resolution means the action buttons (archive_btn, stop_btn, etc., each with their own set_tooltip_text) still take precedence when the pointer is over them, exactly as described in the PR body.

Things I checked and didn't find issues with:

• self._name_label = name_label is stashed before the display-name property binding is set up (sidebar.py:381 vs 535), so the handler always reads the live label.
• get_label() returns the plain bound text (not markup), matching tooltip.set_text — no markup/escaping mismatch.
• The _keyboard param is intentionally unused; the same "still ellipsized?" check is correct for both pointer- and keyboard-triggered tooltip queries.
• GPL modification notice at the top of the file is already updated with today's date, per repo convention.
• CI is green on this PR.

Minor, non-blocking observations

1. path_label also ellipsizes (_ELLIPSIZE_START, sidebar.py:518) but gets no tooltip. If long project paths get truncated in practice, the same pattern could apply there — but that's an easy follow-up, not something this PR needs to cover.
2. No automated test covers the new _on_query_tooltip logic, but there don't appear to be any existing GTK widget-level unit tests for SessionRow in this repo either, so that's consistent with current conventions rather than a gap introduced here.

Nothing here blocks merging — the change is small, correct, and matches the stated intent.