Extend filter_proxy tests: verify /auth/get-token binding fields

- _mockTokenServer now reads and captures the request body instead of
  draining it — Completer type updated to ({HttpRequest, String rawBody})
- Two new tests: assert that url, method, nonce are present in the
  /auth/get-token request body; verify POST requests carry method=POST

48/48 tests pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

k_phone/test/filter_proxy_test.dart

@@ -38,26 +38,29 @@ Future<({HttpServer server, Completer<HttpRequest> completer})> _mockHttp() asyn
 }
 
 // Mock for Component 2's /auth/get-token endpoint.
-// Responds to every request, completing [tokenReq] on the first one.
+// Reads and captures the full request body; completes [tokenReq] on the first call.
-// When [ok] is false, returns 401 with an error payload.
+// When [ok] is false, returns 401.
-Future<({HttpServer server, Completer<HttpRequest> tokenReq})> _mockTokenServer({
+Future<({HttpServer server, Completer<({HttpRequest req, String rawBody})> tokenReq})>
+    _mockTokenServer({
   String token = 'test-bearer-token',
   bool ok = true,
 }) async {
   final server = await HttpServer.bind('127.0.0.1', 0);
-  final c = Completer<HttpRequest>();
+  final c = Completer<({HttpRequest req, String rawBody})>();
   server.listen((req) async {
-    await req.drain<void>();
+    final bb = BytesBuilder(copy: false);
-    if (!c.isCompleted) c.complete(req);
+    await for (final chunk in req) bb.add(chunk);
-    final body = ok
+    final rawBody = utf8.decode(bb.takeBytes());
+    if (!c.isCompleted) c.complete((req: req, rawBody: rawBody));
+    final resp = ok
         ? '{"ok":true,"token":"$token","expires_in":300}'
-        : '{"ok":false,"error":"no active session","login_required":true}';
+        : '{"ok":false,"error":"card not available","login_required":true}';
     req.response
       ..statusCode = ok ? 200 : 401
       ..headers.set('content-type', 'application/json')
-      ..headers.set('content-length', '${body.length}')
+      ..headers.set('content-length', '${resp.length}')
       ..headers.set('connection', 'close')
-      ..write(body);
+      ..write(resp);
     await req.response.close();
   });
   return (server: server, tokenReq: c);
@@ -196,7 +199,7 @@ void main() {
   group('HTTP routing', () {
     late FilterProxy proxy;
     late HttpServer comp2;
-    late Completer<HttpRequest> comp2TokenReq;
+    late Completer<({HttpRequest req, String rawBody})> comp2TokenReq;
     late HttpServer endpoint;
     late Completer<HttpRequest> endpointReq;
     late HttpServer directServer;
@@ -242,11 +245,43 @@ void main() {
         'GET http://127.0.0.1:${endpoint.port}/api HTTP/1.1\r\n'
         'Host: 127.0.0.1:${endpoint.port}\r\n\r\n',
       );
-      final req = await comp2TokenReq.future.timeout(_kTimeout);
+      final (:req, rawBody: _) = await comp2TokenReq.future.timeout(_kTimeout);
       expect(req.method, 'POST');
       expect(req.uri.path, '/auth/get-token');
     });
 
+    test('gated host: /auth/get-token body carries url, method, nonce', () async {
+      await _round(
+        proxy.port,
+        'GET http://127.0.0.1:${endpoint.port}/api?x=1 HTTP/1.1\r\n'
+        'Host: 127.0.0.1:${endpoint.port}\r\n\r\n',
+      );
+      final (:req, :rawBody) = await comp2TokenReq.future.timeout(_kTimeout);
+      expect(req.uri.path, '/auth/get-token');
+      final body = jsonDecode(rawBody) as Map<String, dynamic>;
+      expect(body['url'], contains('/api?x=1'));
+      expect(body['method'], 'GET');
+      expect(body['nonce'], isA<String>());
+      expect((body['nonce'] as String).length, greaterThan(8));
+    });
+
+    test('gated POST: /auth/get-token body carries method POST', () async {
+      const postBody = '{"key":"val"}';
+      await _round(
+        proxy.port,
+        'POST http://127.0.0.1:${endpoint.port}/submit HTTP/1.1\r\n'
+        'Host: 127.0.0.1:${endpoint.port}\r\n'
+        'Content-Type: application/json\r\n'
+        'Content-Length: ${postBody.length}\r\n\r\n'
+        '$postBody',
+      );
+      final (:req, :rawBody) = await comp2TokenReq.future.timeout(_kTimeout);
+      expect(req.uri.path, '/auth/get-token');
+      final body = jsonDecode(rawBody) as Map<String, dynamic>;
+      expect(body['method'], 'POST');
+      expect(body['url'], contains('/submit'));
+    });
+
     test('gated host: request goes directly to endpoint with Bearer token', () async {
       final response = await _round(
         proxy.port,