build: type-check with ty in a pre-commit hook

ty joins the dev dependency group, locked at 0.0.89, and a local
hook runs `uv run ty check` over the whole project whenever Python
files change. [tool.ty.src] limits the check to pqcli/ and tests/,
so agent worktrees under .claude/ are not checked as duplicate
copies of the project.

.pre-commit-config.yaml

@@ -12,6 +12,12 @@ repos:
 
 - repo: local
   hooks:
+  - id: ty
+    name: ty
+    entry: uv run ty check
+    language: system
+    pass_filenames: false
+    types: [python]
   - id: commit-msg-50-72
     name: Commit message 50/72 rule
     entry: python3 .prek/check_commit_msg