fix: show 'Resuming agent...' during loading when resuming

Set isResumingSession early in the init flow so the loading message
correctly shows 'Resuming agent...' instead of 'Creating agent...'

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Co-Authored-By: Letta <noreply@letta.com>

src/index.ts

@@ -479,6 +479,9 @@ async function main() {
           }
         }
 
+        // Set resuming state early so loading messages are accurate
+        setIsResumingSession(!!resumingAgentId);
+
         // If resuming an existing agent, load the exact tools attached to it
         // Otherwise, load a full toolset based on model/toolset preference
         if (resumingAgentId && !toolset) {