docs: add contract.yaml cheatsheet reference and monitor-alert-escalate pattern (#29, #30)

[ghzhost]

Summary

This PR addresses and resolves issues #29 and #30 by providing essential developer documentation and an architectural pattern guide.

Changes Included:

1. docs/contract-reference.md (Closes [Docs] Write a contract.yaml field reference cheatsheet #30):

   • Fast, single-page reference table covering all contract.yaml (v1.1) fields: version/contract_version, system, lifecycle, inputs, outputs, permissions, side_effects, approval_points/approvals, recovery, replay, dependencies, state, observability, risk, and security.
   • Outlines required status, semantics, minimal practical syntax examples, and common pitfalls/mistakes for each field.
   • Includes a minimal valid contract.yaml template passing schema validation with inline comments for rapid onboarding.

2. patterns/monitor-alert-escalate.md (Closes [Pattern] Document the Monitor-Alert-Escalate pattern #29):

   • Comprehensive pattern document for continuous observation, anomaly detection, and human escalation workflows.
   • Follows standard repo pattern format: Intent, When to use it, When NOT to use it, ASCII structure flow, Contract requirements, and Known implementations (competitor-feature-parity-watcher).

Verification:

• All 60 test suite cases (pytest) pass successfully.
• Minimal template verified against scyvera.validate_contract().