Invalid repo filter


`type`	`https://docs.frem.sh/reference/api/errors/invalid-repo-filter`
HTTP status	`400` Bad Request

What it means

The request was malformed, or a field failed validation.

Example detail messages returned with this error:

repo_filter_regex max 255 chars.
repo_filter_regex invalid: {(err as Error).message}
repo_filter_regex rejected ({unsafe}). Simplify the pattern, e.g. “^owner/prefix-.*”.

Correct the repo_filter value - detail names what was wrong.

All fremforge API errors are RFC 9457 problem+json:

{
  "type": "https://docs.frem.sh/reference/api/errors/invalid-repo-filter",
  "title": "Bad Request",
  "status": 400,
  "detail": "..."
}

Branch on type, not on title or detail - those are human-readable and may be reworded.