feat: improve documentation quality with real data

- Extract file-level docstrings from Python files (module-level string expressions)
- Use __init__.py docstrings as module doc_summary
- Use file docstrings as file purpose in layout tables (instead of 'Source file')
- Populate module outbound_modules/inbound_modules from import edges (internal only)
- Make filename sanitization consistent (sanitize_for_link matches sanitize_filename)
- Clean up stale .md files from previous runs before generating
- Fill ARCHITECTURE.md template with real layout, modules index, and critical points
- Add file_docstring field to ParsedModule and file_purpose to FileDoc

test-project/docs/architecture/modules/utils.md

@@ -0,0 +1,92 @@
+# Module: utils
+
+Utility functions for the test project.
+
+## Symbols
+
+### load_config
+
+def load_config(config_path: str)
+
+Load configuration from a JSON file.
+
+**Type:** Function
+
+**Metrics:**
+- Fan-in: 0
+- Fan-out: 2
+
+### save_config
+
+def save_config(config: dict, config_path: str)
+
+Save configuration to a JSON file.
+
+**Type:** Function
+
+**Metrics:**
+- Fan-in: 0
+- Fan-out: 2
+
+### get_file_size
+
+def get_file_size(filepath: str)
+
+Get the size of a file in bytes.
+
+**Type:** Function
+
+**Metrics:**
+- Fan-in: 0
+- Fan-out: 1
+
+### format_bytes
+
+def format_bytes(size: int)
+
+Format bytes into a human-readable string.
+
+**Type:** Function
+
+**Metrics:**
+- Fan-in: 0
+- Fan-out: 0
+
+
+## Dependencies
+
+### Imports
+- json
+- os
+
+### Outbound Modules
+
+### Inbound Modules
+
+## Integrations
+
+
+
+
+## Usage Examples
+
+```python
+from utils import load_config
+result = load_config(config_path)
+```
+
+```python
+from utils import save_config
+result = save_config(config, config_path)
+```
+
+```python
+from utils import get_file_size
+result = get_file_size(filepath)
+```
+
+```python
+from utils import format_bytes
+result = format_bytes(size)
+```
+