feat(intel): clarify firmware/DDC flow and preserve driver metadata

- Add explanatory comments across intel driver to clarify metadata parsing.
- Ensure driver selection preserves runtime options (e.g. "intel/ddc_override:AABB")
  so driver-specific metadata is passed through to the host and available to
  drivers via host.hci_metadata.
- Ensure transport parsing regex and metadata extraction so transport/source
  metadata is populated and visible to drivers.
- Example usage: passing [driver=intel/ddc_override:AABB] will be preserved and
  can be consumed by the Intel driver to apply a DDC override blob.

bumble/transport/__init__.py

@@ -84,7 +84,12 @@ async def open_transport(name: str) -> Transport:
     scheme, *tail = name.split(':', 1)
     spec = tail[0] if tail else None
     metadata = None
-    if spec and (m := re.search(r'\[(\w+=\w+(?:,\w+=\w+)*,?)\]', spec)):
+    # If a spec is provided, check for a metadata section in square brackets.
+    # The regex captures a comma-separated list of key=value pairs (allowing an
+    # optional trailing comma). The key is matched by \w+ and the value by [^,\]]+,
+    # meaning the value may contain any character except a comma or a closing
+    # bracket (']').
+    if spec and (m := re.search(r'\[(\w+=[^,\]]+(?:,\w+=[^,\]]+)*,?)\]', spec)):
         metadata_str = m.group(1)
         if m.start() == 0:
             # <metadata><spec>