fix: improve bootstrap error handling

Improve error handling in bootstrap processes to suppress spurious errors
and handle process exit codes more robustly:

Bootstrap-smol improvements:
- Suppress spurious "command failed" errors during CLI execution
- Extract error message once for reuse
- Only write actual errors to stderr

Node bootstrap improvements:
- Handle signal-based process exits correctly
- Exit with code 1 when child process terminated by signal
- Exit with child's exit code otherwise (or 0 if none)

These changes reduce noise in error output and ensure correct exit
codes are propagated through the bootstrap chain.

Author: jdalton

packages/bootstrap/src/bootstrap-smol.mts

@@ -19,7 +19,12 @@ async function main() {
 
 // Run the bootstrap.
 main().catch((e) => {
+  // Suppress spurious "command failed" error from process.exit() during CLI execution.
+  const errorMsg = e instanceof Error ? e.message : String(e)
+  if (errorMsg.includes('command failed')) {
+    return
+  }
   // Use process.stderr.write() directly to avoid console access during early bootstrap.
-  process.stderr.write(`Bootstrap error: ${e instanceof Error ? e.message : String(e)}\n`)
+  process.stderr.write(`Bootstrap error: ${errorMsg}\n`)
   process.exit(1)
 })

packages/cli/src/bootstrap/node.mts

@@ -146,9 +146,9 @@ async function main(): Promise<void> {
     process.exit(1)
   })
 
-  child.on('exit', code => {
+  child.on('exit', (code, signal) => {
     // eslint-disable-next-line n/no-process-exit
-    process.exit(code ?? 0)
+    process.exit(code ?? (signal ? 1 : 0))
   })
 }