refactor: Clean up test files and simplify documentation

- Remove unused cassette files with incomplete recordings
- Delete broken respx test files (test_o3_pro_respx_simple.py, test_o3_pro_http_recording.py)
- Fix respx references in docstrings to mention HTTP transport recorder
- Simplify vcr-testing.md documentation (60% reduction, more task-oriented)
- Add simplified PR template with better test instructions
- Fix cassette path consistency in examples
- Add security note about reviewing cassettes before committing

🤖 Generated with [Claude Code](https://claude.ai/code)

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

pr_template_filled_simplified.md

@@ -0,0 +1,59 @@
+## PR Title
+
+**fix: Fix o3-pro empty response issue by using output_text field**
+
+## Summary
+
+Fixes o3-pro API calls returning empty responses due to incorrect response parsing. The code was trying to parse `response.output.content[]` array, but o3-pro provides `output_text` directly.
+
+## Changes
+
+- Fixed o3-pro response parsing to use `output_text` field
+- Added `_safe_extract_output_text` method with validation
+- Implemented HTTP transport recorder for testing expensive API calls
+- Added PII sanitization for test recordings
+- Added regression tests
+
+**No breaking changes** - Internal fix only
+
+## Testing
+
+```bash
+source venv/bin/activate
+./code_quality_checks.sh
+
+# Run the new tests added in this PR
+python -m pytest tests/test_o3_pro_output_text_fix.py -v
+python -m pytest tests/test_pii_sanitizer.py -v
+
+# Or run all new tests together
+python -m pytest tests/test_o3_pro_output_text_fix.py tests/test_pii_sanitizer.py -v
+```
+
+- [x] All checks pass
+- [x] Regression tests added:
+  - `test_o3_pro_output_text_fix.py` - Validates o3-pro response parsing and HTTP transport recording
+  - `test_pii_sanitizer.py` - Ensures API key sanitization
+
+## Code Example
+
+**Before:**
+```python
+# Incorrect - manual parsing
+for content_item in response.output.content:
+    if content_item.type == "output_text":
+        content = content_item.text
+```
+
+**After:**
+```python
+# Correct - direct field access
+content = response.output_text
+```
+
+## For Reviewers
+
+- Core fix: `providers/openai_compatible.py` - see `_safe_extract_output_text()` method
+- Response parsing: `_generate_with_responses_endpoint()` method now uses the direct field
+- Test infrastructure changes don't affect production code
+- All test recordings sanitized for security