Add pre-commit hook to verify all CLI commands are documented in README

Extracts commands from the Typer app and checks each has a corresponding
--help section in the README. Runs when README.md or CLI files change.

.pre-commit-config.yaml

@@ -1,4 +1,13 @@
 repos:
+  - repo: local
+    hooks:
+      - id: check-readme-commands
+        name: Check README documents all CLI commands
+        entry: python .github/check_readme_commands.py
+        language: system
+        files: ^(README\.md|src/compose_farm/cli/.*)$
+        pass_filenames: false
+
   - repo: https://github.com/pre-commit/pre-commit-hooks
     rev: v5.0.0
     hooks: