fix(commands): send empty images list to the commands Typert endpoint

The Harness commands execute descriptor declares agentId, line, and images
as required JSON wire fields (strict codec, no acceptsUndefined). The Host
command executor only sent agentId and line, so the Typert gateway rejected
every IM /compact call with arguments-invalid before the command could run.

Send images: [] so /compact works from every IM channel.

plugin-src/host/harness-command-executor.mjs

@@ -15,7 +15,11 @@ export function createHarnessCommandExecutor(ctx, provided) {
   return (sessionId, line, options = {}) => gateway.invoke({
     namespace: 'commands',
     method: 'execute',
-    args: { agentId: sessionId, line },
+    // The Harness commands execute descriptor declares agentId, line, and
+    // images as required JSON wire fields; omitting images makes the Typert
+    // gateway reject the call with arguments-invalid, so IM /compact always
+    // carried an empty image list.
+    args: { agentId: sessionId, line, images: [] },
     signal: options.signal,
   });
 }

test/compact-command.test.mjs

@@ -145,7 +145,10 @@ test('Host command executor invokes the commands Typert endpoint with the Sessio
   assert.deepEqual(requests, [{
     namespace: 'commands',
     method: 'execute',
-    args: { agentId: 'session-one', line: '/compact' },
+    // images must ride the wire as an empty array: the Harness commands
+    // execute descriptor declares it a required JSON field, and omitting it
+    // makes the Typert gateway reject the call with arguments-invalid.
+    args: { agentId: 'session-one', line: '/compact', images: [] },
     signal,
   }]);
   assert.equal(createHarnessCommandExecutor({}), undefined);