Artifact path failures told callers to "inspect the reported path" but
reported none: `ArtifactReaderFailure` messages such as
`Artifact path collision: ...` were dropped when converted to
`ArtifactOperationError`, leaving only `{ operation, reason: "path" }`.
Carry the failure message into `details.detail` for artifact tools and
JavaScript application analysis. Name both spellings in case-fold
collisions and include the JSON-escaped input in unsafe and
non-normalized path messages.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>