Add integration tests for multi-hook scenarios in hookify

Create comprehensive pytest integration test suite for the hookify plugin:

- test_integration.py: Multi-hook evaluation, rule priority (blocking over warnings),
  condition AND logic, tool type field extraction, Stop/UserPromptSubmit events
- test_rule_loading.py: YAML frontmatter parsing, rule file loading, event filtering
- test_error_handling.py: Fault tolerance for missing files, invalid regex, malformed input

Also fix a bug discovered through testing: MultiEdit field extraction now
gracefully handles malformed edit entries (non-dict values in edits array).

68 tests covering:
- Multiple rules combining messages
- Blocking rules taking priority over warnings
- Multiple conditions with AND logic
- Different tool types (Bash, Write, Edit, MultiEdit)
- Stop event transcript checking
- UserPromptSubmit validation
- Tool matcher filtering
- Regex pattern matching and caching
- Error handling and edge cases

https://claude.ai/code/session_014B79JcfZHUaTfnThn3o3g2

plugins/hookify/tests/__init__.py

@@ -0,0 +1 @@
+"""Hookify integration tests."""