feat(query): expose discovery route metadata

[SioYooo]

Summary

• expose discover -> hydrate -> compose query route metadata in CLI and MCP responses
• treat family ids as follow-up handles while keeping show_family exact-family-id only
• sync managed agent instructions, quickstarts, specs, project memory, and ADR-0018

Validation

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo test --workspace --all-features
• cargo run --quiet --bin repo-guard -- check