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/core.md

@@ -0,0 +1,116 @@
+# Module: core
+
+Core module with database and HTTP integrations.
+
+## Symbols
+
+### DatabaseManager
+
+class DatabaseManager
+
+Manages database connections and operations.
+
+**Type:** Class
+
+**Metrics:**
+- Fan-in: 2
+- Fan-out: 4
+
+### DatabaseManager.__init__
+
+def __init__(self, db_path: str)
+
+No documentation available
+
+**Type:** Method
+
+**Metrics:**
+- Fan-in: 0
+- Fan-out: 0
+
+### DatabaseManager.connect
+
+def connect(self)
+
+Connect to the database.
+
+**Type:** Method
+
+**Metrics:**
+- Fan-in: 0
+- Fan-out: 1
+
+### DatabaseManager.execute_query
+
+def execute_query(self, query: str)
+
+Execute a database query.
+
+**Type:** Method
+
+**Metrics:**
+- Fan-in: 0
+- Fan-out: 3
+
+### fetch_external_data
+
+def fetch_external_data(url: str)
+
+Fetch data from an external API.
+
+**Type:** Function
+
+**Metrics:**
+- Fan-in: 2
+- Fan-out: 2
+
+### process_user_data
+
+def process_user_data(user_id: int)
+
+Process user data with database and external API calls.
+
+**Type:** Function
+
+**Metrics:**
+- Fan-in: 0
+- Fan-out: 4
+
+
+## Dependencies
+
+### Imports
+- sqlite3
+- requests
+
+### Outbound Modules
+
+### Inbound Modules
+
+## Integrations
+
+### Database Integrations
+- DatabaseManager
+- DatabaseManager.connect
+
+### HTTP/API Integrations
+- fetch_external_data
+
+
+## Usage Examples
+
+```python
+from core import DatabaseManager
+instance = DatabaseManager()
+```
+
+```python
+from core import fetch_external_data
+result = fetch_external_data(url)
+```
+
+```python
+from core import process_user_data
+result = process_user_data(user_id)
+```
+