feat(WARDEN-WP-0014): T1 — structured handoff fields in routing catalog

Adds optional assist-layer fields (auth_method, path_template,
fetch_command, exec_capable, policy_ref) to RouteEntry, parsed and
secret-screened in catalog.py. Handoff fields are templates/pointers
only — _assert_no_secret_material rejects known token prefixes and
high-entropy runs, and exec_capable requires a fetch_command. The
openbao-api-key entry is populated as the reference example (covers the
coulomb_social npm shape).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/warden/routing/models.py

@@ -26,11 +26,26 @@ class RouteEntry:
     # SSH lane only — None/empty for routed (non-executed) needs.
     steps: List[str] = field(default_factory=list)
     cert_command: Optional[str] = None
+    # Structured handoff (WP-0014) — optional, allowed on any lane. These are
+    # *templates and pointers* the `warden access` assist layer renders (and, for
+    # exec_capable lanes, proxies). They are NOT authored procedure prose and they
+    # never carry a secret value — only placeholders (`<...>`) and field names.
+    # Validation in catalog.py enforces the no-secret-material rule on every one.
+    auth_method: Optional[str] = None       # how the caller authenticates to the owner
+    path_template: Optional[str] = None      # owner-side path with `<...>` placeholders
+    fetch_command: Optional[str] = None      # command skeleton run *as the caller*
+    exec_capable: bool = False               # may `warden access --fetch/--exec` proxy it
+    policy_ref: Optional[str] = None         # flex-auth check the fetch path runs first
 
     @property
     def is_active(self) -> bool:
         return self.status == "active"
 
+    @property
+    def has_handoff(self) -> bool:
+        """True when structured assist fields are present (advisory richness)."""
+        return any((self.auth_method, self.path_template, self.fetch_command))
+
     def match_score(self, tokens: List[str]) -> int:
         """Keyword-overlap score against need_keywords, title, and id.