Fix dispatcher auth under bounded clock skew

[munirad7s]

Summary

• derive a bounded auth clock from the TLS-authenticated relay WSS upgrade (Date, then production cDate)
• apply the offset only to newly signed NIP-42 and NIP-98 events; leave Windows time, ordinary events, and the relay's ±60s verification unchanged
• provision the existing ChatGPT-subscription Codex agent as the no-cost dispatcher with agent-scoped Vault/n8n MCPs through the existing secret shim and the same 17 write denies
• preserve unrelated Codex settings with an idempotent marked config block and rollback copy

Security

• WSS-only, TLS-verified time source
• midpoint calculation, <=30s RTT, <=24h absolute offset
• malformed/missing/out-of-bound samples fail closed to the previous bounded value
• no header, challenge, event, key, token, or credential value is logged or committed
• no API key, paid fallback, Windows clock change, verifier-window change, server deploy, or ordinary event timestamp change

Verification

• cargo test -p buzz-acp relay::tests (86 passed)
• cargo clippy -p buzz-acp --all-targets -- -D warnings
• cargo fmt --all -- --check
• .empire/tools/test/codex-dispatcher-mcp-test.sh
• .empire/tools/test/nest-mcp-secrets-test.sh (6 passed)
• shell syntax checks and diff/secret scan
• full cargo test -p buzz-acp: all new tests plus 672 existing lib tests pass; 23 existing Windows tests fail because they spawn Unix cat, reproduced unchanged on origin/main
• local just ci: affected Rust/workspace and frontend checks pass; Windows Desktop clippy then stops on pre-existing cfg-specific unused/dead-code warnings in untouched Desktop files. CI is the authoritative clean-platform gate.

Closes #3 only after post-merge local rollout and all three exact read-only #agent-lab answers.

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