refactor(claude): derive result status and error together

[rynfar]

Claude turn status and error text were derived from separate lists of failure reasons. Derive them together so future updates cannot classify a stopped turn differently from its explanation. Existing overload, structured failure, interruption, cancellation, and unknown-reason behavior stays intact.

Adopts upstream #10296, 4c7cd17a832269ef17edcf99e987ac25ae1b640a.

Validation: 98 Claude adapter tests pass, including unknown terminal reasons. Server typecheck and scoped lint pass. No contracts or client UI changed.

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	0 B (0.0%)	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	6.7 KiB	6.7 KiB	+4 B (+0.1%)	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	+29 B (+0.2%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	+8 B (+0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.7 KiB	6.7 KiB	+21 B (+0.3%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	58.1 KiB	58.2 KiB	+44 B (+0.1%)	66.4 KiB	✅
Claude	Live turn messages	8	9	+1 (+12.5%)	21	✅

Baseline: 16c999a · PR result: 960977d · 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.