chore: add mypy to pre-commit config and document setup

- Add mypy as a local pre-commit hook via prek (ruff-check + ruff-format
  + mypy now all run at commit time)
- Add Setup section to CLAUDE.md with uv sync and prek install steps

.pre-commit-config.yaml

@@ -2,7 +2,14 @@ repos:
   - repo: https://github.com/astral-sh/ruff-pre-commit
     rev: v0.15.8
     hooks:
-    # Run the linter.
       - id: ruff-check
-    # Run the formatter.
       - id: ruff-format
+
+  - repo: local
+    hooks:
+      - id: mypy
+        name: mypy
+        entry: uv run mypy --non-interactive --config-file pyproject.toml
+        language: system
+        types: [python]
+        require_serial: true

CLAUDE.md

@@ -12,6 +12,13 @@ Discovery -> Ranking -> Context Extraction -> Test Gen + Optimization -> Baselin
 
 See `.claude/rules/architecture.md` for directory mapping and entry points.
 
+## Setup
+
+```bash
+uv sync                  # Install all dependencies
+uv run prek install      # Install git pre-commit hooks (ruff + mypy)
+```
+
 ## Bug Fix Workflow
 
 Follow these steps in order, do not skip ahead: