Keep dev watch alive on initial errors and harden env parsing

- Do not exit dev watch on first compilation error; only reject when
  BUILD_WATCH_ONCE is enabled. This preserves the previous DX of
  staying in watch mode to fix errors.
- Add robust boolean env parsing for BUILD_WATCH_ONCE to treat '0',
  'false', 'no', 'off', and empty as false.
- Retain fast‑fail for early setup/packaging errors and for watch‑once.

Why: Refactor introduced a Promise wrapper that caused dev to exit on
initial compile errors. This change restores expected behavior while
keeping deterministic exits for CI/watch‑once.

Author: PeterDaveHello

build.mjs

@@ -15,7 +15,12 @@ const __dirname = path.resolve()
 const isProduction = process.argv[2] !== '--development' // --production and --analyze are both production
 const isAnalyzing = process.argv[2] === '--analyze'
 const parallelBuild = process.env.BUILD_PARALLEL !== '0'
-const isWatchOnce = !!process.env.BUILD_WATCH_ONCE
+function parseBooleanEnv(val) {
+  if (val == null) return false
+  const s = String(val).trim().toLowerCase()
+  return !(s === '' || s === '0' || s === 'false' || s === 'no' || s === 'off')
+}
+const isWatchOnce = parseBooleanEnv(process.env.BUILD_WATCH_ONCE)
 // Cache compression control: default none; allow override via env
 function parseCacheCompressionOption(envVal) {
   if (envVal == null) return undefined
@@ -598,18 +603,27 @@ async function build() {
 
   await new Promise((resolve, reject) => {
     const ret = runWebpack(false, false, false, outdir, async (err, stats) => {
-      if (err || (stats && typeof stats.hasErrors === 'function' && stats.hasErrors())) {
+      const hasErrors = !!(
+        err ||
+        (stats && typeof stats.hasErrors === 'function' && stats.hasErrors())
+      )
+      if (hasErrors) {
         console.error(err || stats.toString())
-        reject(err || new Error('webpack error'))
+        // In normal dev watch, keep process alive on initial errors; only fail when watch-once
+        if (isWatchOnce) {
+          reject(err || new Error('webpack error'))
+        }
         return
       }
       try {
         await finishOutput('')
         resolve()
       } catch (e) {
+        // Packaging failure should stop even in dev to avoid silent success
         reject(e)
       }
     })
+    // Early setup failures (e.g., dynamic imports) should fail fast
     if (ret && typeof ret.then === 'function') ret.catch(reject)
   })
 }