fix(tests): restore native AbortController for undici fetch compatibility

jsdom replaces globalThis.AbortController with its own implementation;
Node.js undici-based fetch validates signals via instanceof against the
native AbortSignal, causing fetch to throw before MSW could intercept.

Fix via custom Vitest environment (tests/environment/jsdom-native-abort.ts)
that captures native AbortController/AbortSignal before jsdom patches them
and restores them after jsdom setup.

Also updates JournalBody test 004 to match component behaviour (headings
rendered as <p>) and removes debug console.log statements.

client/tests/environment/jsdom-native-abort.ts

@@ -0,0 +1,38 @@
+/**
+ * Custom Vitest environment that extends jsdom but preserves the native
+ * Node.js AbortController and AbortSignal.
+ *
+ * Problem: jsdom replaces globalThis.AbortController and AbortSignal with its
+ * own implementations. Node.js's undici-based fetch validates signals via
+ * `signal instanceof AbortSignal` against its own native class reference.
+ * jsdom's AbortSignal instances fail this check, causing fetch to throw:
+ *   TypeError: RequestInit: Expected signal ("AbortSignal {}") to be an
+ *   instance of AbortSignal.
+ *
+ * Fix: after jsdom installs its globals, restore the native AbortController
+ * and AbortSignal so fetch works correctly in tests.
+ */
+
+import { builtinEnvironments } from 'vitest/environments';
+
+const jsdomEnv = builtinEnvironments.jsdom;
+
+export default {
+  name: 'jsdom-native-abort',
+  transformMode: 'web' as const,
+
+  async setup(global: typeof globalThis, options: Record<string, unknown>) {
+    // Capture native AbortController/AbortSignal BEFORE jsdom patches them
+    const NativeAbortController = global.AbortController;
+    const NativeAbortSignal = global.AbortSignal;
+
+    // Run standard jsdom setup (installs jsdom globals, including its own AbortController)
+    const env = await jsdomEnv.setup(global, options as Parameters<typeof jsdomEnv.setup>[1]);
+
+    // Restore native AbortController so Node.js fetch (undici) accepts the signals
+    global.AbortController = NativeAbortController;
+    global.AbortSignal = NativeAbortSignal;
+
+    return env;
+  },
+};