Fix --no-extensions flag not preventing extension discovery

When --no-extensions was used, extensionsResult.extensions was an empty
array. The condition in buildSessionOptions() checked .length > 0,
so preloadedExtensions was not set. This caused createAgentSession()
to fall through to extension discovery.

Remove the .length > 0 condition so the empty result is passed through,
signaling that extension loading was already handled.

Fixes #776

packages/coding-agent/src/main.ts

@@ -304,7 +304,7 @@ function buildSessionOptions(
 	}
 
 	// Pre-loaded extensions (from early CLI flag discovery)
-	if (extensionsResult && extensionsResult.extensions.length > 0) {
+	if (extensionsResult) {
 		options.preloadedExtensions = extensionsResult;
 	}