test(desktop): make MCP renderer relay regressions executable

evals/desktop_mcp_oauth/README.md

@@ -0,0 +1,19 @@
+# Desktop MCP OAuth integration checks
+
+Run from a checkout with the Python MCP dependencies and Desktop Node dependencies installed.
+Outputs are local receipts; keep them outside the checkout. Neither harness uses real provider credentials.
+
+```bash
+python3 evals/desktop_mcp_oauth/backend_http_fixture.py --repo . --output /tmp/mcp-backend.json
+node evals/desktop_mcp_oauth/renderer_lifecycle.mjs "$PWD" /tmp/mcp-renderer.json approved
+node evals/desktop_mcp_oauth/renderer_lifecycle.mjs "$PWD" /tmp/mcp-scope.json cancel
+node evals/desktop_mcp_oauth/renderer_lifecycle.mjs "$PWD" /tmp/mcp-unmount.json unmount
+```
+
+The backend harness creates disposable HOME/HERMES_HOME directories and a local HTTP OAuth/MCP provider. It exercises production session functions, discovery, dynamic registration, PKCE code exchange, token persistence and fresh-process authenticated MCP access. Wrong state, callback replay, wrong server, wrong profile and cancellation are negative controls. It removes temporary token stores and reports only booleans/paths, never token values.
+
+The renderer harness bundles the real McpTab and its dependencies in Chromium, runs the production native loopback listener with a registration-only Electron IPC adapter, and uses a fixture WebSocket backend. `cancel` changes the component's scope; `unmount` removes it entirely. Both must cancel the original backend session and close its native listener without relaying a callback. `approved` must use the native relay, not REST auth. Set `CHROMIUM_EXECUTABLE` to use an existing Chromium executable; otherwise Playwright's installed browser is used.
+
+These are complementary integration probes, not a single end-to-end Electron/provider test. The renderer backend and Electron registration boundary are fixtures; the Python probe uses production session functions rather than gateway RPC transport. No native Electron application launch or hosted-provider consent is claimed.
+
+For A/B, run the same renderer harness against a baseline checkout by replacing its first positional argument. The approved assertion fails before the shared relay change. For the lifecycle regression, a checkout immediately before the scoped-tab cleanup fails both abandonment assertions. Backend cross-profile callbacks must be rejected even when the session ID and valid state are supplied; the original owner must still be able to finish afterward.

evals/desktop_mcp_oauth/renderer_lifecycle.mjs

@@ -187,6 +187,10 @@ try {
     )
     assert(!rpcCalls.some(m => m.method === 'mcp.servers.oauth.callback'), 'no callback after abandonment')
   }
+  if (scenario === 'approved') {
+    assert(approved && hasScope, 'Skills must complete OAuth through its native listener')
+    assert(!requests.some(r => r.path.endsWith('/auth')), 'native flow must not use REST auth')
+  }
   assert.deepEqual(errors, [])
 } finally {
   await browser.close()