robustness(core): static checks to validate history is immutable (#21228)

packages/sdk/src/session.ts

@@ -226,7 +226,7 @@ export class GeminiCliSession {
         break;
       }
 
-      const transcript: Content[] = client.getHistory();
+      const transcript: readonly Content[] = client.getHistory();
       const context: SessionContext = {
         sessionId,
         transcript,

packages/sdk/src/types.ts

@@ -51,7 +51,7 @@ export interface AgentShell {
 
 export interface SessionContext {
   sessionId: string;
-  transcript: Content[];
+  transcript: readonly Content[];
   cwd: string;
   timestamp: string;
   fs: AgentFilesystem;