feat(ecosystem): hub-core library lane for three-repo stack (HUB-WP-0003)

Add slugify_or_default for core-hub parity, bump to 0.2.0, document ecosystem
position in INTENT/SCOPE/README, wire capability relations to state-hub and
core-hub, and extend utils tests. Part of CUST-WP-0057 consolidation.

hub_core/utils/slugs.py

@@ -12,3 +12,19 @@ def slugify(value: str, *, max_length: int = 100) -> str:
     if max_length < 1:
         raise ValueError("max_length must be >= 1")
     return slug[:max_length].strip("-")
+
+
+def slugify_or_default(
+    value: str,
+    *,
+    default: str = "resource",
+    max_length: int = 100,
+) -> str:
+    """Like slugify but returns default when input yields no slug characters.
+
+    Matches core-hub bootstrap semantics where API consumers need a fallback slug.
+    """
+    try:
+        return slugify(value, max_length=max_length)
+    except ValueError:
+        return default