fix(gitlab): accept only merge request URLs the path parser can read

The reference check let `?` and `#` into the host and allowed one-segment
or empty-segment repositories, so URLs like https://gitlab.com?x=/g/p/-/merge_requests/5
and https://gitlab.com/t3code/-/merge_requests/12 passed it while
CHANGE_REQUEST_PATH returned null. The host now stops at `/?#`, and the
repository needs at least two non-empty segments, matching the parser.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
c52430b516Victor Vogel committed on 10/24/2026, 5:53:50 PMparent6e9591e

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