Add --force flag to reverse sync

Bypasses the PR step and force-pushes the subrepo's state directly onto
the monorepo branch. Also skips the skip-dirty guard. Only valid with
--reverse. Returns status "forced".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/auth.sh

@@ -28,6 +28,16 @@ subrepo_auth_url() {
   fi
 }
 
+# ─── Monorepo Auth URL ─────────────────────────────────────────────
+# Derives a push-capable HTTPS URL from MONOREPO_API.
+# MONOREPO_API shape: https://<host>/api/v1/repos/<org/repo>
+
+mono_auth_url() {
+  local api_host_path
+  api_host_path=$(echo "$MONOREPO_API" | sed 's|https://||; s|/api/v1/repos/|/|')
+  echo "https://${BOT_USER}:${GITEA_TOKEN}@${api_host_path}.git"
+}
+
 # ─── Remote Queries ─────────────────────────────────────────────────
 
 subrepo_ls_remote() {