feat: delegate project register; registrar-only ID minting

STATE-WP-0080-T02: statehub register routes project-flavor scaffolding
through rmgr scaffold and keeps only repo + host-path registration.
T01 refuse remains when GOAL.md is missing and --wp-prefix is not set.

RMGR-WP-0005-T01: C-06/C-11/C-32 skip mint+writeback unless this
instance is the identifier registrar (STATEHUB_REGISTRAR or railiance
hostname).

api/services/repo_manager_dual_run.py

@@ -249,6 +249,55 @@ def rm_update_task_status(
     return result
 
 
+def rm_scaffold(
+    *,
+    repo_path: str | Path,
+    flavor: str,
+    wp_prefix: str | None = None,
+    slug: str | None = None,
+    domain: str = "infotech",
+    force: bool = False,
+    commit: bool = False,
+) -> dict[str, Any]:
+    """Delegate repository scaffolding to ``rmgr scaffold`` (STATE-WP-0080-T02)."""
+    args = [
+        "scaffold",
+        "--path",
+        str(repo_path),
+        "--flavor",
+        flavor,
+        "--domain",
+        domain,
+    ]
+    if slug:
+        args.extend(["--slug", slug])
+    if wp_prefix:
+        args.extend(["--wp-prefix", wp_prefix])
+    if force:
+        args.append("--force")
+    if not commit:
+        args.append("--no-commit")
+    code, out, err = run_rmgr(args)
+    try:
+        result = json.loads(out.strip() or "{}")
+    except json.JSONDecodeError:
+        result = {
+            "status": "failed",
+            "error": {
+                "code": "internal",
+                "message": f"rmgr non-json exit={code} stderr={err!r} stdout={out[:500]!r}",
+            },
+        }
+    if code != 0 and result.get("status") not in ("applied", "rejected"):
+        result.setdefault("status", "failed")
+        result.setdefault(
+            "error",
+            {"code": "internal", "message": f"rmgr exit={code} stderr={err!r}"},
+        )
+    result["exit_code"] = code
+    return result
+
+
 def rm_reconcile(*, repo_path: str | Path, repo_slug: str | None = None) -> dict[str, Any]:
     args = ["reconcile", "--path", str(repo_path)]
     if repo_slug: