perf(web): hidden terminal drawers and typing stop doing idle work

[rynfar]

Two upstream client-performance fixes for work the web app did while idle. Part of #865.

Source	Upstream PR	Disposition
6989856aa630611dd7d6dcc8cfe9f97456816284	#13686	Adopted. Hidden-but-mounted terminal drawers read only the thread shell instead of subscribing to full thread detail, so their history is no longer held in memory. The active drawer keeps detail, which also covers archived threads that have no shell.
ed57bed8e71b2e89a9350c94bda0dacc71cd4817	#13884	Adapted. Shortcut modifier tracking compares against its own copy and skips the React state dispatch when nothing changed, so ordinary typing no longer re-enters the sidebar tree.

Pylon adaptations

• Pylon's web tests have no jsdom, which upstream's render regressions need. Rather than add a DOM test dependency, the guard lives in a small createShortcutModifierTracker that the hook delegates to, and the regressions assert on the tracker: a reset by keyup or by paste/blur, then typing and repeated resets report nothing, and the next real modifier reports exactly once.
• Draft waitForShell/promotion, scoped environment/worktree/PTY metadata, synthetic dictation paste and blur resets, and both sidebars' use of the hook are unchanged.

Verification

• vp test run src/shortcutModifierState.test.ts from apps/web: 7 tests pass.
• vp run -F @t3tools/web typecheck: no errors.
• vp lint / vp fmt --check on the three changed files: no errors (existing set-state-in-effect warnings in ChatView.tsx are on untouched lines).

Limits: no rendered-client pass and no latency measurement; upstream's 195x figure is not claimed for Pylon.

Model: Claude Opus 5.5. Harness: Claude Code in Pylon. Workflow: review-t3-upstream skill.

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

ℹ️ No successful main baseline artifact is available yet. This run establishes the initial measurement.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	—	14.0 KiB	—	15.1 KiB	✅
Codex	Thread snapshot wire	—	7.3 KiB	—	7.3 KiB	✅
Codex	Live turn WebSocket wire	—	6.7 KiB	—	7.8 KiB	✅
Codex	Live turn WebSocket decoded	—	58.0 KiB	—	66.4 KiB	✅
Codex	Live turn messages	—	9	—	21	✅
Claude	Total thread wire	—	14.0 KiB	—	15.1 KiB	✅
Claude	Thread snapshot wire	—	7.3 KiB	—	7.3 KiB	✅
Claude	Live turn WebSocket wire	—	6.7 KiB	—	7.8 KiB	✅
Claude	Live turn WebSocket decoded	—	58.9 KiB	—	66.4 KiB	✅
Claude	Live turn messages	—	9	—	21	✅

Baseline: unavailable · PR result: efeef4d · 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: 115.7 KiB
• Claude decoded thread snapshot: 116.4 KiB

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