feat(cli): add Slack community CTA on errors, crashes, setup, and help (#277)

* feat(cli): show Slack CTA on help and unexpected errors

* feat(cli): show Slack CTA after crashes

* feat(setup): show Slack community note after setup

* chore: refresh Python lockfile versions

packages/cli/test/io/tty.test.ts

@@ -0,0 +1,40 @@
+import { describe, expect, it } from 'vitest';
+
+import { isWritableTtyOutput } from '../../src/io/tty.js';
+
+describe('isWritableTtyOutput', () => {
+  it('accepts writable TTY-like output', () => {
+    const output = {
+      isTTY: true,
+      columns: 80,
+      on: () => undefined,
+      write: () => undefined,
+    };
+
+    expect(isWritableTtyOutput(output)).toBe(true);
+  });
+
+  it('rejects non-TTY output', () => {
+    expect(isWritableTtyOutput({ write: () => undefined })).toBe(false);
+  });
+
+  it('rejects output missing stream event support', () => {
+    expect(
+      isWritableTtyOutput({
+        isTTY: true,
+        columns: 80,
+        write: () => undefined,
+      }),
+    ).toBe(false);
+  });
+
+  it('rejects output missing column metadata', () => {
+    const output = {
+      isTTY: true,
+      on: () => undefined,
+      write: () => undefined,
+    };
+
+    expect(isWritableTtyOutput(output)).toBe(false);
+  });
+});