fix(core): made context files append instead of replace (#26950)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

packages/cli/src/config/config.ts

@@ -16,7 +16,8 @@ import { hooksCommand } from '../commands/hooks.js';
 import { gemmaCommand } from '../commands/gemma.js';
 import {
   setGeminiMdFilename as setServerGeminiMdFilename,
-  getCurrentGeminiMdFilename,
+  resetGeminiMdFilename,
+  DEFAULT_CONTEXT_FILENAME,
   ApprovalMode,
   DEFAULT_GEMINI_EMBEDDING_MODEL,
   DEFAULT_FILE_FILTERING_OPTIONS,
@@ -619,7 +620,7 @@ export async function loadCliConfig(
     setServerGeminiMdFilename(settings.context.fileName);
   } else {
     // Reset to default if not provided in settings.
-    setServerGeminiMdFilename(getCurrentGeminiMdFilename());
+    resetGeminiMdFilename(DEFAULT_CONTEXT_FILENAME);
   }
 
   const fileService = new FileDiscoveryService(cwd);