test(setup): add integration tests and update shell completion

Adds comprehensive integration tests for the first-run wizard verifying config
generation for different provider/channel combinations. Updates shell completion
to include the 'setup' command with its options.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/cli/completion.ts

@@ -3,13 +3,14 @@ import { mkdirSync, writeFileSync } from 'fs';
 import { resolve } from 'path';
 import { homedir } from 'os';
 
-const SUBCOMMANDS = ['start', 'tui', 'send', 'sessions', 'doctor', 'config', 'completion'];
+const SUBCOMMANDS = ['start', 'tui', 'send', 'sessions', 'doctor', 'config', 'setup', 'completion'];
 
 const SUBCOMMAND_OPTIONS: Record<string, string[]> = {
   start: ['-c', '--config'],
   tui: ['-c', '--config', '-f', '--fullscreen'],
   send: ['-c', '--config', '--no-tools'],
   config: ['-c', '--config', '--raw'],
+  setup: ['-c', '--config'],
   completion: ['--install'],
 };