fix(web): restore reverted messages to composer

[amitray007]

What Changed

Reverted user messages now return to the Alpha composer with their available images. If a draft is already present, it is saved to Stash first. The live timeline also removes the reverted message after the server confirms the rewind.

This carries the seven implementation commits from pingdotgg/t3code#6044 without behavioral changes. The combined implementation patch has the same stable patch ID as the upstream PR. An Alpha feature record marks it as temporary and defines its retirement condition.

Why

“Revert to this message” currently rewinds the checkpoint but leaves the selected message in the timeline and forces users to recreate the prompt. The upstream fix is still awaiting review, so Alpha can carry it now and retire the delta after upstream merges an equivalent implementation.

Related

• Related: fix(web): restore reverted messages to composer pingdotgg/t3code#6044
• Related: [Bug]: Revert leaves selected user prompt visible and composer empty pingdotgg/t3code#5685

UI Changes

Before	After

Interaction

bettershot_1786392103024.mp4

Validation

• vp test run apps/web/src/components/ChatView.logic.test.ts packages/client-runtime/src/state/threadReducer.test.ts — 71 tests passed
• vp run --filter @t3tools/web typecheck
• vp run --filter @t3tools/client-runtime typecheck — passed with one existing Effect suggestion
• Targeted vp lint and vp fmt --check
• git diff --check
• Stable patch ID matches the complete upstream PR implementation

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for the UI change
• I included a video for the interaction change

Implemented by GPT-5.6 via the Codex harness in T3 Code.

[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	12.6 KiB	12.6 KiB	+17 B (+0.1%)	15.1 KiB	✅
Codex	Thread snapshot wire	6.3 KiB	6.3 KiB	0 B (0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.3 KiB	6.3 KiB	+17 B (+0.3%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	51.8 KiB	51.8 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	16	16	0 (0.0%)	21	✅
Claude	Total thread wire	12.6 KiB	12.6 KiB	+6 B (+0.0%)	15.1 KiB	✅
Claude	Thread snapshot wire	6.3 KiB	6.3 KiB	−1 B (−0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.3 KiB	6.3 KiB	+7 B (+0.1%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	52.7 KiB	52.7 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	16	16	0 (0.0%)	21	✅

Baseline: 479e527 · PR result: d89b0e8 · 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: 99.9 KiB
• Claude decoded thread snapshot: 100.6 KiB

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