feat(stdlib): new modules + eslint/tsconfig migration

- Add array/async/etc. modules and type tests; migrate to eslint flat config
  and composite tsconfig (vitest typecheck enabled).
- Fix PubSub.emit to snapshot listeners before iterating (stable EventEmitter
  semantics; avoids invoking listeners added during the same emit).

core/stdlib/src/text/trigram-distance/index.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect } from 'vitest';
+import { describe, expect, it } from 'vitest';
 import { trigramDistance, trigramProfile } from '.';
 
 describe('trigramProfile', () => {
@@ -66,6 +66,13 @@ describe('trigramDistance', () => {
     expect(trigramDistance(profile1, profile2)).toBe(1);
   });
 
+  it('is symmetric', () => {
+    const a = trigramProfile('hello world');
+    const b = trigramProfile('hello lorem');
+
+    expect(trigramDistance(a, b)).toBe(trigramDistance(b, a));
+  });
+
   it('one for empty text and non-empty text', () => {
     const profile1 = trigramProfile('hello world');
     const profile2 = trigramProfile('');