feat(setup): auto-detect timezone after CLI agent step

Adds a timezone step between cli-agent and channel wiring in setup:auto.
Autodetect via --step timezone; if it resolves to UTC or fails, confirm
with the user and accept either an IANA zone or a free-text description
(e.g. "New York"). Free-text falls through to a headless `claude -p`
call that returns a single IANA string, gated on the claude CLI being
on PATH.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

setup/lib/claude-assist.ts

@@ -56,6 +56,7 @@ const STEP_FILES: Record<string, string[]> = {
   mounts: ['setup/mounts.ts'],
   service: ['setup/service.ts'],
   'cli-agent': ['setup/cli-agent.ts', 'scripts/init-cli-agent.ts'],
+  timezone: ['setup/timezone.ts', 'setup/lib/tz-from-claude.ts'],
   channel: ['setup/auto.ts'],
   verify: ['setup/verify.ts'],
   // Channel-specific sub-steps:

setup/lib/tz-from-claude.ts

@@ -0,0 +1,126 @@
+/**
+ * Headless Claude fallback for timezone resolution.
+ *
+ * When the user answers the UTC-confirmation prompt with something that
+ * isn't a valid IANA zone ("NYC", "Jerusalem time", "eastern"), spawn
+ * `claude -p` with a narrow prompt asking for a single IANA string and
+ * validate the reply with `isValidTimezone` before returning it.
+ *
+ * Gated on claude being on PATH — if the user did the paste-OAuth or
+ * paste-API auth path they may not have the CLI installed. Returns null
+ * in that case so the caller can ask them to try again with a canonical
+ * zone string.
+ */
+import { execSync, spawn } from 'child_process';
+
+import * as p from '@clack/prompts';
+import k from 'kleur';
+
+import { isValidTimezone } from '../../src/timezone.js';
+import { fitToWidth } from './theme.js';
+
+export function claudeCliAvailable(): boolean {
+  try {
+    execSync('command -v claude', { stdio: 'ignore' });
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+/**
+ * Ask headless Claude to map a free-text location/timezone description to
+ * a valid IANA zone. Shows a spinner with elapsed time. Returns the
+ * resolved zone string on success, or null if the CLI is missing, Claude
+ * errored, or the reply wasn't a valid IANA zone.
+ */
+export async function resolveTimezoneViaClaude(
+  input: string,
+): Promise<string | null> {
+  if (!claudeCliAvailable()) return null;
+
+  const prompt = buildPrompt(input);
+
+  const s = p.spinner();
+  const start = Date.now();
+  const label = 'Looking up that timezone…';
+  s.start(fitToWidth(label, ' (999s)'));
+  const tick = setInterval(() => {
+    const elapsed = Math.round((Date.now() - start) / 1000);
+    const suffix = ` (${elapsed}s)`;
+    s.message(`${fitToWidth(label, suffix)}${k.dim(suffix)}`);
+  }, 1000);
+
+  const reply = await queryClaude(prompt);
+
+  clearInterval(tick);
+  const elapsed = Math.round((Date.now() - start) / 1000);
+  const suffix = ` (${elapsed}s)`;
+
+  const resolved = reply ? extractTimezone(reply) : null;
+  if (resolved) {
+    s.stop(
+      `${fitToWidth(`Interpreted as ${resolved}.`, suffix)}${k.dim(suffix)}`,
+    );
+    return resolved;
+  }
+  s.stop(
+    `${fitToWidth("Couldn't interpret that as a timezone.", suffix)}${k.dim(
+      suffix,
+    )}`,
+    1,
+  );
+  return null;
+}
+
+function buildPrompt(input: string): string {
+  return [
+    'Convert the user\'s description of where they are into a single IANA',
+    'timezone identifier (e.g. "America/New_York", "Europe/London",',
+    '"Asia/Jerusalem"). Respond with ONLY the IANA string on a single line,',
+    'nothing else — no prose, no quotes, no punctuation. If you cannot',
+    'determine a zone with reasonable confidence, reply with exactly:',
+    'UNKNOWN',
+    '',
+    `User's description: ${input}`,
+  ].join('\n');
+}
+
+function queryClaude(prompt: string): Promise<string | null> {
+  return new Promise((resolve) => {
+    const child = spawn('claude', ['-p', '--output-format', 'text'], {
+      stdio: ['pipe', 'pipe', 'pipe'],
+    });
+    let stdout = '';
+    let settled = false;
+    const settle = (value: string | null): void => {
+      if (settled) return;
+      settled = true;
+      resolve(value);
+    };
+
+    child.stdout.on('data', (c: Buffer) => {
+      stdout += c.toString('utf-8');
+    });
+    child.on('close', (code) => {
+      settle(code === 0 && stdout.trim() ? stdout : null);
+    });
+    child.on('error', () => settle(null));
+
+    child.stdin.end(prompt);
+  });
+}
+
+function extractTimezone(reply: string): string | null {
+  // Claude occasionally prefixes with a backtick or wraps in quotes despite
+  // instructions; take the first line that looks like a zone.
+  const lines = reply
+    .split('\n')
+    .map((l) => l.trim().replace(/^["'`]+|["'`]+$/g, ''))
+    .filter(Boolean);
+  for (const line of lines) {
+    if (line === 'UNKNOWN') return null;
+    if (isValidTimezone(line)) return line;
+  }
+  return null;
+}