fix(openrouter): translate the provider on startSession input

[gfsaaser24]

Every OpenRouter turn failed immediately with ProviderAdapterValidationError: Expected provider 'claudeAgent' but received 'openrouter'.

The OpenRouter adapter is the Claude adapter wrapped in an identity decorator. The decorator restamped outputs (sessions, events) to openrouter, but ClaudeAdapter.startSession also validates its input provider and rejects anything that is not its own kind. Orchestration passes provider: 'openrouter', so the call never got past validation.

The decorator now translates the input provider to the wrapped adapter's kind on the way in, and still restamps on the way out. Inputs with no provider are passed through untouched.

Adds a regression test that drives a validating fake adapter; it fails without the fix.

🤖 Generated with Claude Code

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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	—	12.6 KiB	—	15.1 KiB	✅
Codex	Thread snapshot wire	—	6.3 KiB	—	7.3 KiB	✅
Codex	Live turn WebSocket wire	—	6.3 KiB	—	7.8 KiB	✅
Codex	Live turn WebSocket decoded	—	51.8 KiB	—	66.4 KiB	✅
Codex	Live turn messages	—	16	—	21	✅
Claude	Total thread wire	—	12.6 KiB	—	15.1 KiB	✅
Claude	Thread snapshot wire	—	6.3 KiB	—	7.3 KiB	✅
Claude	Live turn WebSocket wire	—	6.3 KiB	—	7.8 KiB	✅
Claude	Live turn WebSocket decoded	—	52.7 KiB	—	66.4 KiB	✅
Claude	Live turn messages	—	16	—	21	✅

Baseline: unavailable · PR result: 002dfe9 · 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.