ci: enable godox, noctx, errname, ireturn linters

[creed-bratton]

Enables four linters that have zero violations in the current codebase.

godox — no TODO/FIXME/HACK/XXX in production code.

noctx — no direct http.Get/http.Post calls; the codebase uses a custom HTTP client throughout.

ireturn — no bare interface returns. MarshalYAML() (any, error) is covered by the default empty allow category.

errname — error types follow the convention. ValidationWarning is the only exception: it is intentionally named as a warning even though it implements error (it signals a non-fatal issue, not an error). A //nolint:errname annotation documents this.

recvcheck, errorlint, err113, wrapcheck will be addressed separately as they need small code fixes.

[bfabio]

@creed-bratton I'm not onboard with the godox rule.

Banning TODO and FIXME outright is harmful IMO. People people will just remove them to make the linter happy and then the information is gone.

[creed-bratton]

Dropped godox per your feedback.

Fixed the remaining violations:

• noctx: replaced p.client.Get with http.NewRequestWithContext + Do
• ireturn: added PublicCode to the allow list in settings -- it is the intended public API return type, not an accidental bare interface
• errname: //nolint on ValidationResults -- renaming to ValidationResultsError would be a breaking API change