refactor(web-panel): update architecture + cheat i18n

Reorganize the panel around product capabilities and integrate the
remote i18n feature from origin/master into the new structure.

- Restructure src into capability features (app, trainer, library,
  remote-session, appearance, shared); move the bridge to bridge/src.
- Add lingui-based UI localization and wrap remaining user-facing
  strings (Trans / msg macros); fix the 'END В·' mojibake.
- Port WeMod cheat-metadata i18n: capture the access token from the
  snapshot's renderer in the bridge and fetch localized trainer_meta
  in remote-session.i18n; guarantee snapshot sync on token failure.
- Wire vitest to the app's lingui/preact pipeline (mergeConfig).

web-panel/protocol/validation.test.ts

@@ -0,0 +1,30 @@
+import { describe, expect, it } from 'vitest';
+
+import { PROTOCOL_VERSION } from './contract';
+import { isIncomingMessage, isOutgoingMessage } from './validation';
+
+describe('web protocol validation', () => {
+  it('rejects messages with another envelope version', () => {
+    expect(isIncomingMessage({
+      type: 'error',
+      version: PROTOCOL_VERSION + 1,
+      requestId: null,
+      payload: { code: 'bad', message: 'bad' },
+    })).toBe(false);
+  });
+
+  it('rejects incomplete required payloads', () => {
+    expect(isIncomingMessage({
+      type: 'hello_ack',
+      version: PROTOCOL_VERSION,
+      requestId: null,
+      payload: { accepted: true },
+    })).toBe(false);
+    expect(isOutgoingMessage({
+      type: 'set_value',
+      version: PROTOCOL_VERSION,
+      requestId: 'set',
+      payload: { target: 'speed', value: 1 },
+    })).toBe(false);
+  });
+});