fix(git-tools): pr-create API fallback resolves base from forge default branch (E4) (#1376)

packages/mosaic/framework/tools/git/test-issue-create-interactive-auth.sh

@@ -67,7 +67,18 @@ cat > "$BIN_DIR/curl" <<'SH'
 #!/usr/bin/env bash
 set -euo pipefail
 printf 'curl %s\n' "$*" >> "$MOSAIC_TEST_LOG"
-printf '%s\n' '{"number":703}'
+# Repo roots: the pr-create API fallback resolves its base from the forge
+# default_branch (T51-P2 WP5a). Exact-suffix so every other endpoint keeps
+# the historical answer below.
+url="${*: -1}"
+case "$url" in
+    */api/v1/repos/mosaicstack/stack)
+        printf '%s\n' '{"default_branch":"next"}'
+        ;;
+    *)
+        printf '%s\n' '{"number":703}'
+        ;;
+esac
 SH
 chmod +x "$BIN_DIR/tea" "$BIN_DIR/curl"