perf: skip pre-compression history on session resume

On resume (-r), the CLI was loading and replaying the entire session
recording, including messages that had already been compressed away.
For long-running Forever Mode sessions this made resume extremely slow.

Add lastCompressionIndex to ConversationRecord, stamped when
compression succeeds. On resume, only messages from that index
onward are loaded into the client history and UI. Fully backward
compatible — old sessions without the field load all messages as before.

packages/cli/src/nonInteractiveCli.ts

@@ -222,6 +222,7 @@ export async function runNonInteractive({
         await geminiClient.resumeChat(
           convertSessionToClientHistory(
             resumedSessionData.conversation.messages,
+            resumedSessionData.conversation.lastCompressionIndex,
           ),
           resumedSessionData,
         );