[codex] Add public MCP timeout transcript

[Atomics-hub]

Summary

• Add public examples/mcp-timeout-session.jsonl and examples/mcp-timeout-server.sh fixtures.
• Add release-audit coverage for a downstream timeout after descriptor mediation and an allowed tool-call boundary.
• Verify the timeout response is sanitized, AgentK metadata is stripped before forwarding, and raw request arguments remain out of output/evidence.

Why

The existing timeout smoke covered a hung downstream response, but it was an internal fixture and timed out before descriptor mediation. This makes the failure mode reviewer-visible in public examples while preserving hash-first evidence.

Verification

• cargo fmt --check
• cargo test release_audit_public_mcp_timeout_transcript_reports_sanitized_timeout -- --nocapture
• cargo test
• cargo clippy --all-targets --all-features -- -D warnings
• cargo run --locked -- release-audit