test(protocol): preserve provider transport diagnostics

[wolfiesch]

Summary

• add an app-wire upgrade sentry for additive provider transport diagnostics
• cover full session lists, direct list decoders, incremental session deltas, and typed list/create responses
• preserve the complete redacted diagnostic object across every session-bearing decode path

Verification

• mise exec node@24.17.0 -- pnpm --filter @t4-code/protocol test
• mise exec node@24.17.0 -- pnpm check
• mise exec node@24.17.0 -- pnpm test (1,481 tests passed)
• git diff --check

[Copilot]

Pull request overview

Adds regression coverage to ensure provider transport diagnostic evidence (liveState.providerTransport) is preserved across all session-bearing decode paths in the @omp/protocol app-wire facade.

Changes:

• Introduces a frozen providerTransport diagnostic fixture used across decode tests.
• Adds tests verifying providerTransport survives decoding through session list frames, session list results, session deltas, and typed response results.

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