fix: use local prettier from package.json and clean up prettierignore

- Replace mirrors-prettier alpha (v4.0.0-alpha.8) with local hook using
  the stable prettier installed via package.json
- Remove .prettierignore entries already handled by the hook's exclude pattern

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.pre-commit-config.yaml

@@ -23,10 +23,13 @@ repos:
       - id: isort
         args: [--settings-path=pyproject.toml]
 
-  - repo: https://github.com/pre-commit/mirrors-prettier
-    rev: v4.0.0-alpha.8
+  - repo: local
     hooks:
       - id: prettier
+        name: prettier
+        entry: npx prettier --write --ignore-unknown
+        language: node
+        types_or: [javascript, ts, json, yaml, markdown]
         exclude: ^(dist/|package-lock\.json|\.venv/|python/)
 
   - repo: https://github.com/pycqa/flake8