chore: sync upstream main through 75d63d64c5

[donnes]

What changed

Merge 56 commits from pingdotgg/t3code through 75d63d64c5 into the fork, preserving the fork's existing commits and features. This brings in upstream server performance improvements, client fixes, observability changes, and the chat width setting.

Resolve the two conflicts in packages/contracts/src/editor.ts and apps/server/src/process/externalLauncher.test.ts by retaining px0 support and its tests alongside upstream's corrected Antigravity IDE commands and tests. Include the lockfile updates generated by vp i. No fork changes were dropped; every file in the saved fork delta remains represented.

Why

Keep the fork current with upstream using a two-parent merge so existing fork history survives. Merge this PR with a merge commit rather than squash or rebase to retain upstream ancestry for future syncs.

Validation

• vp i passed.
• Scoped typechecks passed for server, web, desktop, mobile, client-runtime, contracts, and shared.
• vp test run on the 28 fork test files passed: 853 tests passed, one skipped.
• vp lint passed for both conflict-resolution files.
• git diff --check and the saved fork-delta comparison passed.
• Browser and device verification were not run. UI changes come from the upstream commits.

Model: GPT-6-Astra. Harness: Codex.

[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	−17 B (−0.1%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.1 KiB	7.1 KiB	−4 B (−0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.5 KiB	6.5 KiB	−13 B (−0.2%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	56.3 KiB	56.3 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	10	10	0 (0.0%)	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	+13 B (+0.2%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.5 KiB	6.4 KiB	−10 B (−0.2%)	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: c188299 · PR result: 4bc9420 · 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: 114.7 KiB

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