feat: add ctx.prompt.form() API for multi-field form dialogs

Add PromptFormRequest and PromptFormResponse types to enable plugins to
display forms with multiple input fields. Implement the form() method in
the prompt context and wire up frontend event handling to show and collect
form responses from users.

src-web/lib/initGlobalListeners.tsx

@@ -21,6 +21,7 @@ import { stringToColor } from './color';
 import { generateId } from './generateId';
 import { jotaiStore } from './jotai';
 import { showPrompt } from './prompt';
+import { showPromptForm } from './prompt-form';
 import { invokeCmd } from './tauri';
 import { showToast } from './toast';
 
@@ -47,6 +48,27 @@ export function initGlobalListeners() {
         },
       };
       await emit(event.id, result);
+    } else if (event.payload.type === 'prompt_form_request') {
+      const values = await showPromptForm({
+        id: event.payload.id,
+        title: event.payload.title,
+        description: event.payload.description,
+        inputs: event.payload.inputs,
+        confirmText: event.payload.confirmText,
+        cancelText: event.payload.cancelText,
+      });
+      const result: InternalEvent = {
+        id: generateId(),
+        replyId: event.id,
+        pluginName: event.pluginName,
+        pluginRefId: event.pluginRefId,
+        context: event.context,
+        payload: {
+          type: 'prompt_form_response',
+          values,
+        },
+      };
+      await emit(event.id, result);
     }
   });