fix(git-tools): pr-merge queue guard reads CI status from the BASE repo (fork PRs, B1)

For a fork PR, pr-metadata's headRepository names the fork (e.g.
stack-mos-dt-0/stack), and pr-merge passed it to ci-queue-wait via -R.
Woodpecker posts commit statuses on the BASE repository, so the guard read
statuses:null from the fork and every fork merge aborted with
state=malformed rc=3 (#1215, gate-merge-01 B1; standalone queue-wait
against the base repo returns terminal-success on the same sha). Same
family as d339e8fd.

- pr-metadata.sh: normalize baseRepository from Gitea base.repo.full_name
- pr-merge.sh: pass the BASE repo to the queue guard; head repo remains
  for head-sha identity; origin-repo fallback when metadata carries no
  base repository (correct for same-repo PRs)
- test-pr-merge-fork-ci-status.sh: fork-PR regression, CI-reachable via
  test:framework-shell beside its siblings; asserts the guard NEVER sees
  the fork and gets the base repo, head branch and exact sha
- test-pr-merge-queue-branch.sh: its old -R assertion pinned the fork
  repo, i.e. the bug; now asserts the base repo

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

@@ -128,6 +128,7 @@ BASE_BRANCH="$(printf '%s' "$PR_METADATA" | python3 -c 'import json, sys; print(
 HEAD_BRANCH="$(printf '%s' "$PR_METADATA" | python3 -c 'import json, sys; print((json.load(sys.stdin).get("headRefName") or "").strip())')"
 HEAD_SHA="$(printf '%s' "$PR_METADATA" | python3 -c 'import json, sys; print((json.load(sys.stdin).get("headRefOid") or "").strip())')"
 HEAD_REPO="$(printf '%s' "$PR_METADATA" | python3 -c 'import json, sys; value=json.load(sys.stdin).get("headRepository") or ""; print((value.get("nameWithOwner") or value.get("full_name") or "") if isinstance(value, dict) else str(value).strip())')"
+BASE_REPO="$(printf '%s' "$PR_METADATA" | python3 -c 'import json, sys; value=json.load(sys.stdin).get("baseRepository") or ""; print((value.get("nameWithOwner") or value.get("full_name") or "") if isinstance(value, dict) else str(value).strip())')"
 PR_TITLE="$(printf '%s' "$PR_METADATA" | python3 -c 'import json, sys; print((json.load(sys.stdin).get("title") or "").strip())')"
 PR_AUTHOR="$(printf '%s' "$PR_METADATA" | python3 -c 'import json, sys; value=json.load(sys.stdin).get("author") or ""; print((value.get("login") or "").strip() if isinstance(value, dict) else str(value).strip())')"
 if [[ "$BASE_BRANCH" != "main" && "$BASE_BRANCH" != "next" ]]; then
@@ -144,10 +145,19 @@ if [[ -n "$EXPECT_HEAD" && "$HEAD_SHA" != "$EXPECT_HEAD" ]]; then
 fi
 
 if [[ "$DRY_RUN" != true ]]; then
+    # CI statuses for a PR live on the BASE repo (Woodpecker posts there),
+    # even when the head branch lives in a fork. Reading status against the
+    # fork repo yields statuses:null -> malformed for every fork PR (#1215,
+    # gate-merge-01 B1). The head repo is used only for head-sha identity;
+    # when metadata carries no base repository, the origin repo is where CI
+    # posts and remains correct for same-repo PRs.
+    if [[ -z "$BASE_REPO" ]]; then
+        BASE_REPO="$(get_repo_owner)/$(get_repo_name)"
+    fi
     "$SCRIPT_DIR/ci-queue-wait.sh" \
         --purpose merge \
         -B "$HEAD_BRANCH" \
-        -R "$HEAD_REPO" \
+        -R "$BASE_REPO" \
         --sha "$HEAD_SHA" \
         -t "${MOSAIC_CI_QUEUE_TIMEOUT_SEC:-900}" \
         -i "${MOSAIC_CI_QUEUE_POLL_SEC:-15}"