fix(server): keep rejected Claude prompts out of running turns

[rynfar]

An unreadable Claude image attachment could fail sendTurn after the adapter had already emitted turn.started and marked the session running. No prompt reached the SDK, so the thread appeared to wait indefinitely and a later message was steered into that empty turn.

Prepare the prompt before changing turn or recovery state, and recheck session ownership after asynchronous preparation and provider setup. This keeps rejected sends out of the runtime queue and rejects sends that finish after a session stop. Regression tests cover missing attachments and stop during provider setup.

Validation: vp test run apps/server/src/provider/Layers/ClaudeAdapter.test.ts (176 passed); vp lint apps/server/src/provider/Layers/ClaudeAdapter.ts apps/server/src/provider/Layers/ClaudeAdapter.test.ts; vp run -F t3 typecheck.

Built with GPT-6 Sol low in the Codex harness.

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Project	Deployment	Actions	Updated
pylon-marketing	Ignored	Preview	Sep 24, 2026 7:28am UTC

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Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	14.0 KiB	13.9 KiB	−20 B (−0.1%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.2 KiB	7.2 KiB	+3 B (+0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.8 KiB	6.7 KiB	−23 B (−0.3%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	58.0 KiB	58.0 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	9	9	0 (0.0%)	21	✅
Claude	Total thread wire	14.0 KiB	14.0 KiB	−8 B (−0.1%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.2 KiB	7.2 KiB	+4 B (+0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.7 KiB	6.7 KiB	−12 B (−0.2%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	58.9 KiB	58.9 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	9	9	0 (0.0%)	21	✅

Baseline: 3868597 · PR result: dc772e5 · 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: 115.6 KiB
• Claude decoded thread snapshot: 116.3 KiB

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