[Kaap10]

Add first-class runtime adapter guide and discovery references for Cursor (Composer in IDE + cursor-agent CLI) per RFC-AI-0004.

Summary

• Adds docs/adapters/cursor.md runtime operating guide for Cursor Composer and cursor-agent CLI.
• Documents runtime contract: skill discovery via canonical .agents/skills/, HITL / Auto-Run approval mapping, MCP tool connectivity, and agent-iso wrapper.
• Updates adapter discovery registry (docs/adapters/registry.md), contributor guide (CONTRIBUTING.md), prerequisites (docs/prerequisites.md), and vendor-neutrality matrix (docs/vendor-neutrality.md).

Type of change

• Skill change (.claude/skills/<name>/) — eval fixtures updated below
• Tool / bridge contract (tools/<system>/*.md)
• Python package (tools/*/ with pyproject.toml)
• Groovy reference impl
• Cross-cutting (RFC, AGENTS.md, sandbox, privacy-LLM)
• Documentation (docs/, README.md, CONTRIBUTING.md)
• Project template (projects/_template/)
• CI / dev loop (prek, workflows, validators)
• Other:

Test plan

• prek run --all-files (or individual hooks: doctoc, add-license-headers) passes
• uv run --project tools/vendor-neutrality-score vendor-neutrality-score passes 100% (10/10 capability contracts, 24/24 substrate tools harness-neutral)
• uv run --project tools/skill-and-tool-validator skill-and-tool-validate passes with 0 errors
• For Python packages touched: uv run pytest / ruff check / mypy passes
• For Groovy bridges touched: command-line invocation tested end-to-end
• For skill changes: eval suite passes for the affected skill
• For skill behaviour changes: a new or updated eval fixture is included in this PR

RFC-AI-0004 compliance

• HITL — maps Cursor's per-action approval modals to Magpie's proposal-then-confirm pattern; restricts destructive Auto-Runs
• Sandbox — integrates with the agent-iso clean-environment wrapper
• Vendor neutrality — adheres to the canonical .agents/skills/ universal discovery path
• Conversational + correctable — agentic-override path documented if behaviour is adopter-tunable
• Write-access discipline — no autonomous outbound messages; drafts only, sent on confirmation
• Privacy LLM — private content does not reach a non-approved LLM; redactor invoked where needed

Linked issues

Closes #316

Notes for reviewers (optional)

Follows the exact 5-step pattern in docs/adapters/add-a-harness.md and aligns with docs/adapters/gemini.md and docs/adapters/codex.md.