update FatalUntrustedWorkspaceError message to include doc link (#25874)

docs/cli/trusted-folders.md

@@ -117,6 +117,10 @@ the following methods:
 These methods will trust the current workspace for the duration of the session
 without prompting.
 
+For detailed instructions on managing folder trust within CI/CD workflows,
+review the
+[Gemini CLI trust guidance for GitHub Actions](https://github.com/google-github-actions/run-gemini-cli/blob/main/docs/trust-guidance.md).
+
 ## Overriding the trust file location
 
 By default, trust settings are saved to `~/.gemini/trustedFolders.json`. If you

packages/cli/src/utils/userStartupWarnings.ts

@@ -96,7 +96,9 @@ const folderTrustCheck: WarningCheck = {
 
     if (isHeadlessMode()) {
       throw new FatalUntrustedWorkspaceError(
-        'Gemini CLI is not running in a trusted directory. To proceed, either use `--skip-trust`, set the `GEMINI_CLI_TRUST_WORKSPACE=true` environment variable, or trust this directory in interactive mode.',
+        'Gemini CLI is not running in a trusted directory. To proceed, either use `--skip-trust`, ' +
+          'set the `GEMINI_CLI_TRUST_WORKSPACE=true` environment variable, or trust this directory in interactive mode. ' +
+          'For more details, see https://geminicli.com/docs/cli/trusted-folders/#headless-and-automated-environments',
       );
     }