<!-- Add the related story/sub-task/bug number, like Resolves#123, or
remove if NA -->
**Related issue:** Fixes#46643
BaseClient.URL() built request paths as `URLPrefix + path`, overwriting
any path already present in BaseURL. Orbit and Fleet Desktop parse the
full fleet URL (subpath included) into BaseURL and pass an empty
URLPrefix, so the subpath was discarded and every API call 404'd when
Fleet was deployed at https://host/subpath. Preserve BaseURL.Path as a
prefix on each request. fleetctl is unaffected since it carries the
subpath in URLPrefix with an empty BaseURL.Path, and non-subpath
deployments are unchanged.
# Checklist for submitter
If some of the following don't apply, delete the relevant line.
- [X] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
See [Changes
files](https://github.com/fleetdm/fleet/blob/main/docs/Contributing/guides/committing-changes.md#changes-files)
for more information.
## Testing
- [X] Added/updated automated tests
- [x] QA'd all new/changed functionality manually
## fleetd/orbit/Fleet Desktop
- [x] Verified compatibility with the latest released version of Fleet
(see [Must
rule](https://github.com/fleetdm/fleet/blob/main/docs/Contributing/workflows/fleetd-development-and-release-strategy.md))
- [x] Verified that fleetd runs on macOS, Linux and Windows
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Bug Fixes**
* Fixed API request URL construction for deployments hosted under a
subpath, preventing broken requests and 404 errors.
* Preserved query parameters when generating request URLs.
* Improved resolution of request paths with and without a leading slash
when combined with a base URL subpath.
* **Documentation**
* Added clearer guidance on how base URL subpaths and additional path
prefixes are combined.
* **Tests**
* Expanded URL-generation coverage to verify correct behavior across
subpath and prefix combinations.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Resolves#40396.
No changes file because there should be no user visible changes.
## Testing
- [x] QA'd all new/changed functionality manually
## fleetd/orbit/Fleet Desktop
- [x] Verified compatibility with the latest released version of Fleet
(see [Must
rule](https://github.com/fleetdm/fleet/blob/main/docs/Contributing/workflows/fleetd-development-and-release-strategy.md))
- [X] Verified that fleetd runs on macOS, Linux and Windows
- [X] Verified auto-update works from the released version of component
to the new version (see [tools/tuf/test](../tools/tuf/test/README.md))
Juan Fernandez