fix(acp): publish reliable turn lifecycle state

[jaxxon33]

Summary

• Clear this agent identity’s orphaned working reactions at harness startup with a bounded query and signed deletion events before subscriptions begin.
• Add a stable typed reason to every turn_error observer payload while preserving the raw adapter code and diagnostic text.
• Classify only narrow operator-actionable diagnostics (auth, quota, model, transient provider); adapter-specific numeric codes cannot mislabel unrelated failures.
• Cover both changes through the production observer and signed REST bridge seams.

Related issue

None found after searching block/buzz issues and pull requests for stale ACP reactions and turn_error reasons.

Testing

• cargo test -q -p buzz-acp: 946 passed, 1 ignored; pool_lifecycle_state: 9 passed.
• cargo fmt --all -- --check: passed.
• cargo clippy -p buzz-acp --all-targets -- -D warnings: passed.
• just ci: attempted; repository-wide clippy could not start because this host lacks pkg-config and OpenSSL development headers. No code failure was reported before that environment dependency stopped the gate.

[github-actions]

🔐 Codex Security Review

Status: review required for the current range.

The current range is ef2aa1ae38fadcc0bc22b8bf6ed96b35933146be...d47d3dc4ae25eab2fa4d056110b52e607918e697.
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