test: add suites for state/sessions, recentSearches, upload (+17)

Via subagent, all verified against real behavior:
- state/sessions (5): fallback-session round-trip across the four cinny_* keys,
  missing-key → undefined for each required key, removeFallbackSession clears all.
- state/recentSearches (6): addRecentSearch prepend, case-sensitive dedupe +
  move-to-front, trim, ignore empty/whitespace, cap at 10.
- state/upload (6): the createUploadAtom reducer driven through a real jotai
  store — idle→loading→progress(gated)→success/error, file ref preserved.

No bugs found.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/state/sessions.test.ts

@@ -0,0 +1,74 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { setFallbackSession, removeFallbackSession, getFallbackSession } from './sessions';
+
+// The fallback-session helpers read/write specific `cinny_*` keys directly on
+// `localStorage`. node has none, so install a controllable in-memory mock per
+// case backed by a Map.
+const installStorage = (): Map<string, string> => {
+  const store = new Map<string, string>();
+  (globalThis as { localStorage?: unknown }).localStorage = {
+    getItem: (key: string) => (store.has(key) ? store.get(key) : null),
+    setItem: (key: string, value: string) => {
+      store.set(key, String(value));
+    },
+    removeItem: (key: string) => {
+      store.delete(key);
+    },
+  };
+  return store;
+};
+
+test('setFallbackSession writes the cinny_* keys', () => {
+  const store = installStorage();
+  setFallbackSession('token-1', 'DEVICE1', '@alice:example.org', 'https://hs.example.org');
+
+  assert.equal(store.get('cinny_access_token'), 'token-1');
+  assert.equal(store.get('cinny_device_id'), 'DEVICE1');
+  assert.equal(store.get('cinny_user_id'), '@alice:example.org');
+  assert.equal(store.get('cinny_hs_base_url'), 'https://hs.example.org');
+});
+
+test('getFallbackSession round-trips a full session and flags fallback stores', () => {
+  installStorage();
+  setFallbackSession('token-1', 'DEVICE1', '@alice:example.org', 'https://hs.example.org');
+
+  assert.deepEqual(getFallbackSession(), {
+    baseUrl: 'https://hs.example.org',
+    userId: '@alice:example.org',
+    deviceId: 'DEVICE1',
+    accessToken: 'token-1',
+    fallbackSdkStores: true,
+  });
+});
+
+test('getFallbackSession returns undefined when nothing is stored', () => {
+  installStorage();
+  assert.equal(getFallbackSession(), undefined);
+});
+
+test('getFallbackSession returns undefined when a single key is missing', () => {
+  // Every one of the four keys is required; missing any one yields undefined.
+  const keys = [
+    'cinny_access_token',
+    'cinny_device_id',
+    'cinny_user_id',
+    'cinny_hs_base_url',
+  ] as const;
+
+  keys.forEach((missing) => {
+    installStorage();
+    setFallbackSession('token-1', 'DEVICE1', '@alice:example.org', 'https://hs.example.org');
+    localStorage.removeItem(missing);
+    assert.equal(getFallbackSession(), undefined, `missing ${missing} should yield undefined`);
+  });
+});
+
+test('removeFallbackSession clears all keys', () => {
+  const store = installStorage();
+  setFallbackSession('token-1', 'DEVICE1', '@alice:example.org', 'https://hs.example.org');
+  removeFallbackSession();
+
+  assert.equal(store.size, 0);
+  assert.equal(getFallbackSession(), undefined);
+});