## What changed
- Add `ToolCallSource` to extension `ToolCall`s and propagate direct or Code Mode
invocation metadata, including the runtime cell and nested tool-call IDs.
- Add `ToolCall::response_byte_budget` so extension tools can bound direct-call
responses by the host truncation policy while allowing Code Mode responses up
to the tool's own limit.
- Share the skills extension's response-size limit between its `list` and `read`
tools.
## Testing
- Verify that Code Mode source metadata is preserved when core constructs an
extension tool call.
GitOrigin-RevId: b10aef01be30d35b67bee3af24a1a4175c9ee112