Implement Phase 3 trigger plane

[G9Pedro]

Summary

• add normalized trigger event, subscription-state, and trigger-receipt contracts plus graph/doc updates for the Phase 3 trigger plane
• refactor wg-trigger into a source-agnostic event evaluator with durable receipt persistence, replay-safe deduplication, and policy-aware action outcomes
• wire post-write trigger ingestion through thread, mission, run, checkpoint, and generic CLI mutation paths
• add CLI trigger workflows (validate, replay, ingest) plus status/brief/output/discovery updates for trigger health and receipt visibility
• align connector/webhook placeholder contracts with the new normalized event model

Verification

• cargo fmt --all
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo test --workspace