feat(web): reset right panel width on double click

[t3-code]

problem

right panels can be resized but have no quick way back to their default width. this reimplements #11219 on current main, preserving the newer per-thread width storage and drag cleanup.

change

• double-click the existing divider to restore the current clamped default width.
• clear only that panel's storage key so future mounts can use a viewport-dependent default.
• shared PreviewPanelShell consumers inherit the behavior, including thread, pull-request, preview and device panels in web and desktop. native mobile is unchanged.

verification

• regression test failed before implementation, then all 16 hook tests passed.
• web typecheck, targeted lint, formatting and git diff --check passed.
• chromium exercised the actual PreviewPanelShell with app styles: dragged width 704px, double-click reset to 540px, storage key removed, reload remained 540px.
• evidence below is a source component preview, not a full authenticated app session. hosted externally; no evidence assets are committed.

before reset

after reset

interaction recording

https://t3bot-uploads-production.up.railway.app/files/ZzM1aXrNcxPvvTXp0FVs5nCb/right-panel-reset.webm

credit

thanks to @cmaciasjimenez for the original contribution in #11219. this replacement preserves their co-author credit. requested by @extoci, also credited as co-author.

implemented with gpt-6-astra using hermes agent.

[macroscopeapp]

Approvability

Verdict: Approved at 1668639

Macroscope's review found this PR approvable — The PR adds a small, self-contained double-click interaction to restore an existing panel width default and clear only that panel’s persisted override. Existing resizing and other panel modes remain unchanged, and targeted tests cover the new behavior.

^{You can add or adjust custom eligibility rules. Learn more.}

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.5 KiB	13.5 KiB	+53 B (+0.4%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.1 KiB	7.1 KiB	−3 B (−0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.4 KiB	6.5 KiB	+56 B (+0.9%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	56.2 KiB	56.3 KiB	+44 B (+0.1%)	66.4 KiB	✅
Codex	Live turn messages	9	10	+1 (+11.1%)	21	✅
Claude	Total thread wire	13.5 KiB	13.5 KiB	+3 B (+0.0%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	+3 B (+0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.4 KiB	6.4 KiB	0 B (0.0%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.0 KiB	57.0 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	9	9	0 (0.0%)	21	✅

Baseline: 9946541 · PR result: 1668639 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 114.0 KiB
• Claude decoded thread snapshot: 114.6 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.