feat(core,cli): harden headless mode detection and align mocks

- Update isHeadlessMode in packages/core to check both stdin.isTTY and stdout.isTTY.
- Synchronize isHeadlessMode mock in packages/cli tests and add global TTY stubs to ensure consistent test environments.
- Add isMounted guard to useFolderTrust hook to prevent state updates on unmounted components in headless mode.
- Expand unit tests in packages/core to cover new TTY check combinations and edge cases.
- Stabilize flaky MCP initialization test in packages/core/src/config/config.test.ts by using a deterministic promise.
- Address review findings regarding environment detection consistency and CI indicator checks.

packages/cli/src/config/trustedFolders.ts

@@ -13,6 +13,7 @@ import {
   ideContextStore,
   GEMINI_DIR,
   homedir,
+  isHeadlessMode,
 } from '@google/gemini-cli-core';
 import type { Settings } from './settings.js';
 import stripJsonComments from 'strip-json-comments';
@@ -282,6 +283,10 @@ export function isWorkspaceTrusted(
   workspaceDir: string = process.cwd(),
   trustConfig?: Record<string, TrustLevel>,
 ): TrustResult {
+  if (isHeadlessMode()) {
+    return { isTrusted: true, source: undefined };
+  }
+
   if (!isFolderTrustEnabled(settings)) {
     return { isTrusted: true, source: undefined };
   }