fix(ui): isMacOS always returned false on Macs + plugin-logic tests (+49)

Coverage work found a 3rd real bug: isMacOS() compared os.name against the
legacy 'Mac OS' string, but ua-parser-js v2 reports 'macOS' — so it was dead,
and Mac users saw "Ctrl + k" instead of "⌘ + k" in the editor toolbar, search,
and settings shortcut hints. Now accepts both 'macOS' and 'Mac OS'.

Suites (via subagent, verified): via-servers (10 — power/popularity server
selection), bad-words (9), syntaxHighlight tokenize (14), plugins/utils
getEmoticonSearchStr (5), imageCompression formatFileSize/isCompressible (5),
user-agent (6, now asserting the fixed behavior).

Full suite now 501 tests, all passing.

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

src/app/plugins/via-servers.test.ts

@@ -0,0 +1,137 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { Room } from 'matrix-js-sdk';
+import { getViaServers } from './via-servers';
+
+type StubEvent =
+  | {
+      content: Record<string, unknown>;
+      sender?: string;
+    }
+  | undefined;
+
+type RoomStub = {
+  members: string[];
+  create?: StubEvent;
+  power?: StubEvent;
+};
+
+const makeRoom = (opts: RoomStub): Room => {
+  const stateEvents: Record<string, StubEvent> = {};
+  if (opts.create) stateEvents['m.room.create'] = opts.create;
+  if (opts.power) stateEvents['m.room.power_levels'] = opts.power;
+
+  const mkEvent = (e: StubEvent) =>
+    e
+      ? {
+          getContent: () => e.content,
+          getSender: () => e.sender,
+        }
+      : undefined;
+
+  return {
+    getMembers: () => opts.members.map((userId) => ({ userId })),
+    getLiveTimeline: () => ({
+      getState: () => ({
+        getStateEvents: (type: string) => mkEvent(stateEvents[type]),
+      }),
+    }),
+  } as unknown as Room;
+};
+
+test('with no power user it returns the top 3 most-populated servers, descending', () => {
+  const room = makeRoom({
+    // s3 x2, s1 x2, s2 x1, s4 x1 — order between equal counts follows insertion
+    members: ['@a:s1.com', '@b:s1.com', '@c:s2.com', '@d:s3.com', '@e:s3.com', '@f:s4.com'],
+  });
+  assert.deepEqual(getViaServers(room), ['s1.com', 's3.com', 's2.com']);
+});
+
+test('the highest-power user server is placed first, ahead of the populous servers', () => {
+  const room = makeRoom({
+    // s3 is most populous (3), but the power user is on s2
+    members: ['@a:s1.com', '@b:s1.com', '@c:s2.com', '@d:s3.com', '@e:s3.com', '@f:s3.com'],
+    power: { content: { users: { '@c:s2.com': 100 }, users_default: 0 } },
+  });
+  // power-user server first, then the top populated servers, s2 deduped
+  assert.deepEqual(getViaServers(room), ['s2.com', 's3.com', 's1.com']);
+});
+
+test('a power-user server that is also the most populous is deduped, result capped at 3', () => {
+  const room = makeRoom({
+    members: [
+      '@a:s1.com',
+      '@b:s1.com',
+      '@c:s1.com',
+      '@d:s2.com',
+      '@e:s3.com',
+      '@f:s4.com',
+      '@g:s5.com',
+    ],
+    power: { content: { users: { '@a:s1.com': 100 }, users_default: 0 } },
+  });
+  // s1 (power + most pop) first, then next 2 of the top-3 populated list
+  assert.deepEqual(getViaServers(room), ['s1.com', 's2.com', 's3.com']);
+});
+
+test('picks the user with the strictly highest power level', () => {
+  const room = makeRoom({
+    members: ['@low:s1.com', '@high:s2.com', '@c:s3.com'],
+    power: {
+      content: {
+        users: { '@low:s1.com': 50, '@high:s2.com': 100 },
+        users_default: 0,
+      },
+    },
+  });
+  assert.equal(getViaServers(room)[0], 's2.com');
+});
+
+test('ignores users whose power is not above users_default', () => {
+  const room = makeRoom({
+    members: ['@a:s1.com', '@b:s2.com'],
+    // @a power equals users_default, so it is not treated as a power user
+    power: { content: { users: { '@a:s1.com': 50 }, users_default: 50 } },
+  });
+  // falls back to populated servers only
+  assert.deepEqual(getViaServers(room), ['s1.com', 's2.com']);
+});
+
+test('uses the create-event sender when the room version supports creators', () => {
+  const room = makeRoom({
+    members: ['@a:s1.com', '@b:s2.com', '@c:s2.com'],
+    create: { content: { room_version: '12' }, sender: '@a:s1.com' },
+    // power levels would point elsewhere, but creatorsSupported short-circuits
+    power: { content: { users: { '@c:s2.com': 100 }, users_default: 0 } },
+  });
+  assert.equal(getViaServers(room)[0], 's1.com');
+});
+
+test('falls back to power levels when the room version does not support creators', () => {
+  const room = makeRoom({
+    members: ['@a:s1.com', '@b:s2.com', '@c:s2.com'],
+    create: { content: { room_version: '11' }, sender: '@a:s1.com' },
+    power: { content: { users: { '@c:s2.com': 100 }, users_default: 0 } },
+  });
+  assert.equal(getViaServers(room)[0], 's2.com');
+});
+
+test('ignores members with unparseable user ids when counting populations', () => {
+  const room = makeRoom({
+    members: ['@a:s1.com', 'broken-id', '@b:s1.com', '@c:s2.com'],
+  });
+  assert.deepEqual(getViaServers(room), ['s1.com', 's2.com']);
+});
+
+test('returns an empty array for a room with no resolvable servers', () => {
+  const room = makeRoom({ members: ['broken-id', 'also-broken'] });
+  assert.deepEqual(getViaServers(room), []);
+});
+
+test('result never exceeds three servers', () => {
+  const room = makeRoom({
+    members: ['@a:s1.com', '@b:s2.com', '@c:s3.com', '@d:s4.com', '@e:s5.com'],
+    power: { content: { users: { '@a:s1.com': 100 }, users_default: 0 } },
+  });
+  assert.ok(getViaServers(room).length <= 3);
+});