fix: refuse to scaffold prj- repos from statehub register

STATE-WP-0080-T01: detect project flavor from classification, GOAL.md,
or a prj- slug, then exit pointing at rmgr scaffold. Durable-repo
write path is unchanged. Rebind 0080 hub IDs to the live workstream
and open T02 now that RMGR-WP-0004-T03 has landed.

statehub_register.py

@@ -15,11 +15,18 @@ from datetime import date
 from pathlib import Path
 from typing import Any
 
+import yaml
+
 
 STATE_HUB_DIR = Path(__file__).resolve().parent
 API_BASE = os.environ.get("API_BASE", "http://127.0.0.1:8000")
 RULES_TEMPLATES_DIR = STATE_HUB_DIR / "scripts" / "project_rules"
 
+from api.classification import (  # noqa: E402
+    CLASSIFICATION_FILENAME,
+    extract_classification_block,
+    load_classification_document,
+)
 from scripts.ensure_gitignore_claude_rules import ensure_claude_gitignore  # noqa: E402
 
 KEY_CONTEXT_FILES = [
@@ -60,12 +67,87 @@ class RegisterInference:
     current_state: str | None = None
 
 
+_FRONTMATTER_RE = re.compile(r"\A---\s*\n(.*?)\n---", re.DOTALL)
+
+
+def detect_project_flavor_signal(
+    project_path: Path,
+    repo_slug: str | None = None,
+) -> str | None:
+    """Return the first project-flavor signal, or None for durable repos.
+
+    Precedence matches repo-manager: classification category, GOAL.md
+    ``repo_flavor``, then a ``prj-`` slug prefix. Any match is enough to
+    refuse scaffolding here (STATE-WP-0080-T01).
+    """
+    category = _classification_category(project_path)
+    if category == "project":
+        return f"{CLASSIFICATION_FILENAME} category=project"
+
+    goal_flavor = _goal_repo_flavor(project_path)
+    if goal_flavor == "project":
+        return "GOAL.md repo_flavor=project"
+
+    for candidate in (repo_slug, project_path.name):
+        if not candidate:
+            continue
+        slug = _slugify(candidate)
+        if slug.startswith("prj-"):
+            return f"slug prefix prj- ({slug})"
+    return None
+
+
+def refuse_project_flavor_scaffold(
+    project_path: Path,
+    repo_slug: str | None = None,
+) -> None:
+    """Exit before writing INTENT.md / PRJ-WP- files into a project repo."""
+    signal = detect_project_flavor_signal(project_path, repo_slug)
+    if signal is None:
+        return
+    raise SystemExit(
+        "ERROR: statehub register refuses to scaffold a project-flavor repository.\n"
+        f"  Detected via: {signal}\n"
+        "  Durable-repo registration is unchanged. Scaffold project repos with Repo Manager:\n"
+        f"    rmgr scaffold --path {project_path} --flavor project --wp-prefix <PREFIX>-WP\n"
+        "  Choose --wp-prefix from the project identity, never PRJ-WP-."
+    )
+
+
+def _classification_category(project_path: Path) -> str | None:
+    doc = load_classification_document(project_path / CLASSIFICATION_FILENAME)
+    block = extract_classification_block(doc)
+    if not block:
+        return None
+    raw = block.get("category")
+    return str(raw).strip().lower() if raw else None
+
+
+def _goal_repo_flavor(project_path: Path) -> str | None:
+    path = project_path / "GOAL.md"
+    if not path.is_file():
+        return None
+    match = _FRONTMATTER_RE.match(_read_limited(path, 4000))
+    if not match:
+        return None
+    try:
+        frontmatter = yaml.safe_load(match.group(1)) or {}
+    except yaml.YAMLError:
+        return None
+    if not isinstance(frontmatter, dict):
+        return None
+    raw = frontmatter.get("repo_flavor")
+    return str(raw).strip().lower() if raw else None
+
+
 def run_register(args: argparse.Namespace) -> None:
     project_path = Path(args.path).expanduser().resolve()
     if not project_path.is_dir():
         print(f"ERROR: {project_path} is not a directory.")
         sys.exit(1)
 
+    refuse_project_flavor_scaffold(project_path, args.repo_slug)
+
     snapshot = collect_repo_snapshot(project_path)
     print(f"==> Inspecting repo at {snapshot.path}")
 
@@ -75,6 +157,7 @@ def run_register(args: argparse.Namespace) -> None:
 
     inference = infer_registration(snapshot, args, domain_slugs)
     repo_slug = args.repo_slug or inference.repo_slug or _slugify(snapshot.project_name)
+    refuse_project_flavor_scaffold(project_path, repo_slug)
     wp_prefix = args.wp_prefix or inference.workplan_prefix or _default_wp_prefix(repo_slug)
     domain = args.domain or inference.domain_slug or _detect_domain_from_files(snapshot)
     project_description = (