fix(desktop): select the WSL route source address - #5889

💭 I'm examining the modified file to check if it follows the established conventions. Looking at the import conventions in the diff — the test file is adding a namespace import from the unstable process subpath, which aligns with the convention of importing Effect library modules as namespaces from their subpaths, so that appears consistent with the existing patterns. The behavioral changes look sound: the backend logic has been refactored and focused tests have been added to cover it. The test uses Effect.provideService to inject the spawner dependency, which is the right approach. Exporting internal implementations like getDistroIpImpl and parsing helpers for testing isn't forbidden by the conventions. There's a notable change in the comments though — the old explanation about wslhost forwarding flakiness was removed and replaced with a new rationale that describes the updated behavior, which represents a shift in the documented reasoning for why the distro IP approach is used. I'm checking whether the layer still uses getDistroIpImpl and verifying that the mirrored networking mode mapping mentioned in the orchestrator comment is actually implemented, though that's not a convention violation. I'm noticing a conflict between the instruction to respond with just "All clear" and the requirement that the final response be JSON. I should follow the schema requirement and structure the response as JSON while including the "All clear" message in the appropriate field.