feat(cli): fixyourdocs init + fixyourdocs report (P0-04)

[mstopa]

Summary

• Adds the Python half of the FixYourDocs CLI as a console_script. Mirrors fixyourdocs/sdk-typescript#5:
  • pipx run fixyourdocs init — appends the canonical AGENTS.md block to AGENTS.md / CLAUDE.md / .cursor/rules / .github/copilot-instructions.md. Idempotent.
  • pipx run fixyourdocs report --doc-url … --summary … --agent … — sends a Docs Feedback Protocol v0 report via Client.send.
• Snippet content is vendored in src/fixyourdocs/snippet.py to match the TypeScript SDK byte-for-byte.
• Exit codes: 0 success, 2 user error, 1 transport / server error. --version, --help, and --json are supported.

Implements the Python steps of P0-04.

Test plan

• ruff check . && mypy src/fixyourdocs && pytest -q — green locally on Python 3.13.
• fixyourdocs --version prints 0.1.0.
• fixyourdocs --help prints usage; fixyourdocs bogus exits 2.
• In an empty dir, fixyourdocs init creates AGENTS.md with the canonical block; second run reports "no changes".
• fixyourdocs init --json prints { path, changed, created }.
• fixyourdocs report --doc-url … --summary … --agent claude-code --api-url <mock> posts a v0 report and prints the returned id (covered by tests/test_cli.py with respx).

Follow-ups not addressed here

• Snippet drift CI (P0-04 step 6 verification): a workflow that fetches the upstream agents-md-snippet README and SHA-checks both SDKs against it. Skipped pending P0-07.
• End-to-end against the deployed Hub (P0-04 "Done when"): blocked on P0-08 / P0-09. Unit and integration coverage here use respx.