feat(google): allow operator headers on Gemini web search (#115549)

* feat(google): support Gemini web search headers

* fix(google): validate Gemini search headers

* docs(changelog): credit Gemini headers

* test(secrets): route config contracts through collector

* chore: remove release-owned changelog entry

* test(google): cover resolved search headers

docs/reference/secretref-credential-surface.md

@@ -50,6 +50,7 @@ The lists below are generated from the source target registry and checked agains
 - `plugins.entries.firecrawl.config.webFetch.apiKey`
 - `plugins.entries.google-meet.config.realtime.providers.*.apiKey`
 - `plugins.entries.google.config.webSearch.apiKey`
+- `plugins.entries.google.config.webSearch.headers.*`
 - `plugins.entries.xai.config.webSearch.apiKey`
 - `plugins.entries.moonshot.config.webSearch.apiKey`
 - `plugins.entries.perplexity.config.webSearch.apiKey`

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

@@ -633,6 +633,13 @@
       "secretShape": "secret_input",
       "optIn": true
     },
+    {
+      "id": "plugins.entries.google.config.webSearch.headers.*",
+      "configFile": "openclaw.json",
+      "path": "plugins.entries.google.config.webSearch.headers.*",
+      "secretShape": "secret_input",
+      "optIn": true
+    },
     {
       "id": "plugins.entries.minimax.config.webSearch.apiKey",
       "configFile": "openclaw.json",