test(web): cancel pending highlight frames before restoring globals

[rynfar]

File-editor highlighting tests can finish successfully and then fail CI when a queued worker broadcast runs after browser globals have been removed. Cancel the fixture’s remaining animation frames after its real workers terminate, and keep the existing highlighting assertions.

Adopts pingdotgg/t3code#10188 (f8b4c464b4760d73e0ece7e68011c738803d8b69). The controlled regression reproduces cancelAnimationFrame is not defined when frame cancellation is removed; all 8 tests pass with the fix. Web typecheck, scoped lint, formatting, and diff checks pass. Production behavior is unchanged, so client screenshots do not apply.

Model: GPT-6 Astra. Harness: Codex.

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[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	13.8 KiB	13.8 KiB	+20 B (+0.1%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.1 KiB	7.1 KiB	+6 B (+0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.7 KiB	6.7 KiB	+14 B (+0.2%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	57.4 KiB	57.4 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	10	10	0 (0.0%)	21	✅
Claude	Total thread wire	13.8 KiB	13.8 KiB	+21 B (+0.1%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	+7 B (+0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.7 KiB	6.7 KiB	+14 B (+0.2%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	58.2 KiB	58.2 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	10	10	0 (0.0%)	21	✅

Baseline: a3b48fc · PR result: 789f51a · 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: 111.2 KiB
• Claude decoded thread snapshot: 111.9 KiB

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