[agent-harness] P2.1 Harness action tiers doc + curl examples

[ManintheCrowds]

Phase 1 — P2.1

Outcome: docs/ page describing trust tiers for harness actions (read-only vs mutate vs shell), mapped to ARCHITECTURE_REST_CONTRACT.md.

Seed: P2 backlog

Acceptance criteria

• At least one curl example per tier against OpenGrimoire base URL pattern.
• Cross-link from AGENT_INTEGRATION.md.

[ManintheCrowds]

Repo naming: Canonical policy and checklist — docs/engineering/OPENGRIMOIRE_NAMING_AND_URLS.md (GitHub ManintheCrowds/OpenGrimoire, local folder OpenGrimoire).