Fix sg docker re-exec restarting setup from scratch

When maybeReexecUnderSg() re-launches setup:auto under `sg docker`,
the new process had no memory of completed steps — it re-prompted the
welcome menu, re-ran environment and container checks, and then failed
on onecli because the earlier run's state was lost.

Pass NANOCLAW_SKIP with completedStepNames() so the re-exec'd process
skips already-finished steps, suppress the welcome menu and existing-env
prompts on re-exec since the user already answered them.

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

setup/auto.ts

@@ -85,7 +85,10 @@ async function main(): Promise<void> {
 
   // Welcome menu — default path or open advanced overrides before any setup
   // work begins. Default lands on standard so Enter is the happy path.
-  const startChoice = ensureAnswer(
+  // On sg re-exec, the user already chose — skip straight to standard.
+  let startChoice: 'default' | 'advanced' = 'default';
+  if (process.env.NANOCLAW_REEXEC_SG !== '1') {
+    startChoice = ensureAnswer(
       await brightSelect<'default' | 'advanced'>({
         message: 'How would you like to begin?',
         options: [
@@ -96,6 +99,7 @@ async function main(): Promise<void> {
       }),
     ) as 'default' | 'advanced';
     setupLog.userInput('start_choice', startChoice);
+  }
   if (startChoice === 'advanced') {
     configValues = await runAdvancedScreen(configValues);
     applyToEnv(configValues);
@@ -126,12 +130,17 @@ async function main(): Promise<void> {
   // paste credentials again on a re-run.
   const existingEnv = detectExistingEnv();
   if (existingEnv) {
+    // On sg re-exec, auto-reuse — the user already decided in the first run.
+    const isReexec = process.env.NANOCLAW_REEXEC_SG === '1';
+    let reuseChoice: 'reuse' | 'fresh' = 'reuse';
+
+    if (!isReexec) {
       const lines = Object.values(existingEnv.groups).map(
         (g) => `  ${k.green('✓')} ${g.label}`,
       );
       note(lines.join('\n'), 'Found existing configuration');
 
-    const reuseChoice = ensureAnswer(
+      reuseChoice = ensureAnswer(
         await brightSelect({
           message: 'Use this existing environment?',
           options: [
@@ -142,6 +151,7 @@ async function main(): Promise<void> {
         }),
       ) as 'reuse' | 'fresh';
       setupLog.userInput('existing_env_choice', reuseChoice);
+    }
 
     if (reuseChoice === 'reuse') {
       for (const [key, value] of Object.entries(existingEnv.raw)) {
@@ -1178,9 +1188,11 @@ function maybeReexecUnderSg(): void {
   if (spawnSync('which', ['sg'], { stdio: 'ignore' }).status !== 0) return;
 
   p.log.warn('Docker socket not accessible in current group. Re-executing under `sg docker`.');
+  const existingSkip = (process.env.NANOCLAW_SKIP ?? '').split(',').map((s) => s.trim()).filter(Boolean);
+  const skipList = [...new Set([...existingSkip, ...setupLog.completedStepNames()])].join(',');
   const res = spawnSync('sg', ['docker', '-c', 'pnpm run setup:auto'], {
     stdio: 'inherit',
-    env: { ...process.env, NANOCLAW_REEXEC_SG: '1' },
+    env: { ...process.env, NANOCLAW_REEXEC_SG: '1', ...(skipList ? { NANOCLAW_SKIP: skipList } : {}) },
   });
   process.exit(res.status ?? 1);
 }