feat(WARDEN-WP-0019): route secret-exec lanes to secrets-engine (route-primary, proxy fallback)

secrets-engine (SECRETS-WP-0003) shipped a native secret-exec front door
(`secrets-engine route/exec`, decision e6381a56) and asked ops-warden to route to it.
Bernd's call: route-primary, proxy-fallback — surface the secrets-engine exec as the
primary path for owned lanes, keep `warden access --exec` as a transparent fallback.

T1 — RouteEntry gains exec_owner/exec_command/pointer_command (+ has_native_exec),
screened for secret material like the other handoff fields. whynot-design-npm-publish
points its native exec at secrets-engine. `warden access` renders Primary (secrets-engine
exec) + Fallback (warden proxy); route/access JSON gain the fields and a native-exec-aware
next_action. Tests added; 217 pass, lint clean.

T2 — credential-routing.md adds secrets-engine as the secret-exec owner (route primary,
proxy fallback); SCOPE adds secrets-engine to Related Repos and records the npm lane as
production-exercised (@whynot/design@0.4.0); playbook leads with secrets-engine exec and
fixes the fallback one-liner (--field NPM_AUTH_TOKEN, --no-policy) per whynot-design.

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

src/warden/cli.py

@@ -556,6 +556,17 @@ def _entry_summary(entry) -> dict:
         # resolvable: can `warden access --fetch` run this now with no <…> to fill?
         # Lets an automated caller gate on readiness before attempting a fetch.
         "resolvable": entry.resolvable,
+        # Owner-native exec front door (WP-0019): when present, this subsystem's exec is
+        # the PRIMARY path; ops-warden's proxy is the transparent fallback.
+        **(
+            {
+                "exec_owner": entry.exec_owner,
+                "exec_command": entry.exec_command,
+                "pointer_command": entry.pointer_command,
+            }
+            if entry.has_native_exec
+            else {}
+        ),
         "wiki_ref": entry.wiki_ref,
         "canon_ref": entry.canon_ref,
         "reviewed": entry.reviewed,
@@ -677,6 +688,11 @@ def route_show(
         if entry.warden_executes:
             summary["steps"] = entry.steps
             summary["cert_command"] = entry.cert_command
+        elif entry.has_native_exec:
+            summary["next_action"] = (
+                f"primary: run via {entry.exec_owner} — `{entry.exec_command}`; ops-warden "
+                f"routes to the owner (fallback: `warden access <need> --exec`). See `{entry.wiki_ref}`."
+            )
         elif entry.exec_capable:
             summary["next_action"] = (
                 f"ops-warden can proxy this as the caller: `warden access <need> --fetch`"
@@ -756,6 +772,12 @@ def _access_json(entry, expanded, gate: str, domain: Optional[str]) -> dict:
     if entry.warden_executes:
         payload["next_action"] = "ops-warden issues this directly — see cert_command"
         payload["cert_command"] = entry.cert_command
+    elif entry.has_native_exec:
+        payload["next_action"] = (
+            f"primary: run via {entry.exec_owner} — `{entry.exec_command}`; "
+            "ops-warden routes to the owner (fallback: `warden access <need> --exec`). "
+            "ops-warden holds no token."
+        )
     elif expanded.exec_capable:
         verb = "fetch" if entry.lane != "login" else "login"
         payload["next_action"] = (
@@ -994,22 +1016,39 @@ def access(
     console.print(f"  wiki     : {entry.wiki_ref}")
     console.print(f"  canon    : {entry.canon_ref}")
 
-    if expanded.exec_capable:
-        proxy = f"warden access {need!r}"
-        if domain:
-            proxy += f" --domain {domain}"
-        hint = (
-            "add --fetch to proxy as the caller"
-            if entry.lane != "login"
-            else "add --fetch to run the interactive login as the caller"
+    proxy = f"warden access {need!r}"
+    if domain:
+        proxy += f" --domain {domain}"
+
+    if entry.has_native_exec:
+        console.print(
+            f"  exec     : [bold]{entry.exec_command}[/bold]  "
+            f"[cyan](via {entry.exec_owner} — primary)[/cyan]"
         )
-        console.print(f"  proxy    : [dim]{proxy} --fetch[/dim]  [yellow]({hint})[/yellow]")
+        if entry.pointer_command:
+            console.print(f"  pointer  : [dim]{entry.pointer_command}[/dim]")
+    if expanded.exec_capable:
+        label = "fallback" if entry.has_native_exec else "proxy"
+        hint = (
+            "transparent conduit — fetches as you"
+            if entry.lane != "login"
+            else "runs the interactive login as you"
+        )
+        console.print(f"  {label:<8} : [dim]{proxy} --fetch[/dim]  [yellow]({hint})[/yellow]")
     if expanded.path_template and "<" in expanded.path_template:
         console.print(
             "  note     : remaining <…> placeholders are owner-confirmed names "
             f"(coordinate with {entry.owner_repo})."
         )
-    if expanded.exec_capable:
+
+    if entry.has_native_exec:
+        console.print(
+            f"\n[green]Primary:[/green] run it via [bold]{entry.exec_owner}[/bold] — "
+            f"[bold]{entry.exec_command}[/bold]. ops-warden routes to the owner and holds no token.\n"
+            f"[dim]Fallback:[/dim] [bold]{proxy} --exec -- <cmd>[/bold] — ops-warden's transparent "
+            "conduit (runs the fetch as you, holds nothing)."
+        )
+    elif expanded.exec_capable:
         verb = "fetch this for you" if entry.lane != "login" else "run this login for you"
         console.print(
             f"\n[green]ops-warden can {verb}[/green] as the caller — "