Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@cmd/api/app_test.go`:
- Line 300: The linter fails because there is no blank line before the recorder
declaration after creating the request; add a single blank line between the
request := httptest.NewRequestWithContext(...) statement and the recorder
declaration (e.g., recorder := httptest.NewRecorder()) so the wsl whitespace
rule is satisfied and the build passes.

In `@cmd/api/app.go`:
- Line 396: Add a blank line immediately before the conditional that checks
cfg.Taxonomy.HubInternalAPIToken (the if statement starting with "if
cfg.Taxonomy.HubInternalAPIToken != \"\"") to satisfy the wsl linter; locate
this conditional in app.go (around the handler/initialization section where cfg
is used) and insert a single empty line above it so the linter no longer flags
missing whitespace.

In `@internal/api/handlers/taxonomy_internal_handler.go`:
- Around line 17-23: Update the doc comment on the AuthCheck method of
TaxonomyInternalHandler to state that authentication is enforced by middleware
rather than by this handler; specifically, change the comment to indicate
AuthCheck simply returns a 200 OK JSON confirming successful
authentication/authorization (the actual token validation is performed by
middleware.Auth applied to the route), and ensure the comment references the
middleware.Auth enforcement and the AuthCheck handler name so readers understand
responsibility separation.

In `@internal/service/taxonomy_client.go`:
- Around line 15-18: Add a godoc comment immediately above the exported error
ErrTaxonomyServiceURLRequired describing what it means and when it is returned
(e.g., "ErrTaxonomyServiceURLRequired is returned when the TAXONOMY_SERVICE_URL
environment variable is not set."); place the comment above the var block (next
to ErrTaxonomyServiceTokenRequired if desired) so the documentation generator
picks it up and the intent of ErrTaxonomyServiceURLRequired is clear.
- Around line 58-88: Define a package-level sentinel error (e.g.,
ErrTaxonomyNon2xx) near the top of the file and replace the dynamic error
returned in TaxonomyClient.StartRun when resp.StatusCode is not 2xx with a
wrapped error that uses the sentinel (for example, fmt.Errorf("%w: taxonomy
service returned status %d", ErrTaxonomyNon2xx, resp.StatusCode)); this
preserves a stable sentinel for error checks while still including the status
code as diagnostic context.