feat(setup): add zero-token /magpie-status Claude Code mod command (part of #1497)

[Kaap10]

Summary

• Zero-token status command (Pilot 2 of Explore Claude Code mods across the skill families #1497): Implemented /magpie-status in plugins/magpie-setup using Claude Code's mod system ($.command.register and command.run), rendering the adoption and health dashboard instantly with zero LLM turns and zero tokens consumed.
• Deterministic collector parity & vendor neutrality: Mod executes the canonical collect_status.py via $.process.run (supporting --format md default and --format json / --format=json / --json overrides, with automatic python3 -> python fallback). This avoids duplicating 770+ lines of Python adoption logic in TypeScript while keeping the universal /magpie-setup status skill 100% operational for non-Claude harnesses.
• Cross-platform robustness: Defensively ensured UTF-8 stdout reconfiguration in collect_status.py against Windows console cp1252 encoding errors, and normalized path separators in drift-check.test.ts for cross-platform mock matching.

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: Claude Code mod / plugin command (plugins/magpie-setup/hooks/)

Test plan

• check-claude-mods script (tools/dev/check-claude-mods.sh) passes:
  • claude plugin validate --strict plugins/magpie-setup passes with zero errors.
  • claude plugin test plugins/magpie-setup passes all 19 tests across 2 files (9 in drift-check.test.ts, 10 in status-command.test.ts).
• For Python packages touched:
  • uv run pytest plugins/magpie-setup/skills/status/tests/ passes all 18 tests (100%).
  • uv run ruff check plugins/magpie-setup/skills/status/scripts/collect_status.py passes with zero violations.
  • uv run ruff format --check plugins/magpie-setup/skills/status/scripts/collect_status.py passes (already formatted).
• Git hygiene:
  • git diff --check passes with zero whitespace or line-ending warnings.
  • End-to-end CLI tested: verified both collect_status.py --format md --repo . and --format json --pretty --repo . execute cleanly.

RFC-AI-0004 compliance

• HITL — /magpie-status is strictly read-only; mutation remains gated via the setup skill.
• Sandbox — No unsandboxed background daemons, no network requests; subprocess executes an argument array directly without a shell.
• Vendor neutrality — The universal Markdown workflow (/magpie-setup status) remains completely functional for non-Claude harnesses (Gemini CLI, Codex, Cursor).
• Conversational + correctable — agentic-override path documented if behaviour is adopter-tunable
• Write-access discipline — Read-only telemetry; no autonomous outbound messages or file mutations.
• Privacy LLM — Pure local deterministic execution; no data sent to external models.

Linked issues

Refs #1497 (Pilot 2)

Notes for reviewers (optional)

• Single Source of Truth: Rather than reimplementing adoption and symlink parsing logic in TypeScript, the mod executes collect_status.py deterministically via $.process.run.
• Static AST Analysis Constraint: Claude Code's static analyzer prohibits passing $ across imported module boundaries. Hook registration (session.start and command.run) lives directly in drift-check.ts (keeping hooks/hooks.json to a single module entrypoint), while execution logic is delegated to the pure, testable executeMagpieStatus helper in status-command.ts.
• Path Normalization in Tests: drift-check.test.ts was updated to normalize Windows backslashes (\) to / in mock path endsWith checks so that the plugin test suite passes locally on Windows as well as in CI.
• Defensive Unicode Handling: collect_status.py now defensively reconfigures stdout encoding to UTF-8 (try...except) to prevent charmap encode exceptions on Windows cp1252 terminals when rendering status indicator emojis.

[Kaap10]

Ready for review!
Implemented Pilot 2 zero-token /magpie-status mod with test coverage.