fix(tools/git): pr-review.sh _belongs case-insensitive repo-slug compare

#866 hardened the comment-persistence read-back into a full-path _belongs()
check that pins scheme+host+port origin plus the full path, to block
look-alike-host and same-host decoy-prefix attacks. That check compared the
path case-sensitively: EXPECTED_REPO_SLUG is taken verbatim from
GITEA_API_BASE and can be mixed-case (e.g. "USC/uconnect"), while Gitea
canonicalizes the returned pull_request_url's owner/repo segment to
lowercase. A successful 201 write on a mixed-case-slug repo therefore
false-negatived ("did not land on a pull request") even though the comment
genuinely landed — fail-closed on a real success, not a false success, but
broken for legitimate mixed-case-slug repos.

Lowercase both sides of the path comparison inside _belongs (path and
expected_path) while leaving the origin tuple comparison, _origin_and_path's
scheme+host lowercasing, and the full (non-suffix) path match untouched — the
look-alike-host and decoy-prefix protections from #866 are unchanged; only
the repo-slug segment's case sensitivity is relaxed, which is safe because
Gitea repo slugs are case-insensitive and the remainder of the path is
numeric.

Adds a red-first regression case (comment-mixed-case-slug) modeling a
mixed-case EXPECTED_REPO_SLUG against a Gitea-canonicalized lowercase
pull_request_url, which fails against pre-fix code and passes after.

Closes #875

packages/mosaic/framework/tools/git/pr-review.sh

@@ -203,7 +203,15 @@ try:
         if not url:
             return False
         origin, path = _origin_and_path(url)
-        return origin == base_origin and path == expected_path
+        # Repo owner/repo slugs are case-insensitive (Gitea canonicalizes the
+        # pull_request_url slug to lowercase on return), while EXPECTED_REPO_SLUG
+        # is taken verbatim from GITEA_API_BASE and may be mixed-case. The
+        # remainder of the path (".../pulls/<number>") is numeric, so lowercasing
+        # the whole path for this comparison only relaxes case, not identity: the
+        # origin tuple (scheme+host+port) above still pins the provider host, and
+        # the path is still compared in FULL (no endswith/suffix match), so the
+        # look-alike-host and same-host decoy-prefix protections are unchanged.
+        return origin == base_origin and path.lower() == expected_path.lower()
 
     if comment.get("id") != expected_id:
         raise ValueError("read-back id does not match the created id")