fix(xai): make x_search auth plugin-owned (#59691)

* fix(xai): make x_search auth plugin-owned

* fix(xai): restore x_search runtime migration fallback

* fix(xai): narrow legacy x_search auth migration

* fix(secrets): drop legacy x_search target registry entry

* fix(xai): no-op knob-only x_search migration fallback

docs/reference/secretref-credential-surface.md

@@ -39,7 +39,6 @@ Scope intent:
 - `plugins.entries.firecrawl.config.webSearch.apiKey`
 - `plugins.entries.tavily.config.webSearch.apiKey`
 - `tools.web.search.apiKey`
-- `tools.web.x_search.apiKey`
 - `gateway.auth.password`
 - `gateway.auth.token`
 - `gateway.remote.token`

docs/reference/secretref-user-supplied-credentials-matrix.json

@@ -523,13 +523,6 @@
       "path": "tools.web.search.apiKey",
       "secretShape": "secret_input",
       "optIn": true
-    },
-    {
-      "id": "tools.web.x_search.apiKey",
-      "configFile": "openclaw.json",
-      "path": "tools.web.x_search.apiKey",
-      "secretShape": "secret_input",
-      "optIn": true
     }
   ]
 }