chore(claude-code): add project agent and quality-check hook config

Add the Explore subagent definition and a PostToolUse hook that runs
Ruff and ty on Python file edits, plus the settings.json wiring it in.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.claude/settings.json

@@ -0,0 +1,20 @@
+{
+  "enabledPlugins": {
+    "astral@astral-sh": true
+  },
+  "hooks": {
+    "PostToolUse": [
+      {
+        "matcher": "Write|Edit",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "repo=$(git rev-parse --show-toplevel 2>/dev/null || pwd); python3 \"$repo/.claude/hooks/python_quality.py\"",
+            "timeout": 120,
+            "statusMessage": "Running Ruff and ty on Python edit"
+          }
+        ]
+      }
+    ]
+  }
+}