feat(abi): adopt canonical AgentState, AgentEvent, and protocol IDs with CI sibling resolution

[aien-dev]

Technical Summary

• Adopt canonical types from aien-agent-state-abi and aien-protocol-types across aegis-runtime.
• Implement bidirectional conversions for SessionId, RunId, ActionId, ApprovalId, and EventId.
• Implement Session::to_agent_state() and AegisEvent::to_canonical_agent_event() with deterministic SHA-256 state digest calculation.
• Add comprehensive unit tests in tests/canonical_abi_tests.rs.
• Configure CI workflow with sibling dependency checkouts for aien-protocols and aien-sovereign-core.

Verification Proof

• cargo test: 80 passed, 0 failed.
• Zero Plaintext Disk Secrets Invariant: Verified.
• Sovereign Voice and Anti-Slop Invariant: Verified (zero em/en dashes).