refactor(sea): remove buildSeaBlob, let binject handle blob generation

Removed the buildSeaBlob() function that was generating SEA blobs
using the host Node.js (e.g., v25.5.0) to generate blobs for
node-smol targets (e.g., v24.10.0).

binject now handles blob generation automatically when --sea points
to a .json config file, using the target binary's Node.js version.
This is critical for useCodeCache support since code cache is
version-specific.

Changes:
- Removed buildSeaBlob() from builder.mjs (50+ lines)
- Updated test-sea.mjs to pass configPath instead of blobPath
- Added explanatory comments about config-based blob generation

Author: jdalton

packages/cli/scripts/sea-build-utils/builder.mjs

@@ -88,56 +88,18 @@ export async function generateSeaConfig(entryPoint, outputPath) {
 // c8 ignore stop
 
 // =============================================================================
-// Section 2: SEA Blob Generation.
+// Section 2: SEA Blob Generation (handled by binject).
 // =============================================================================
 
-/**
- * Build SEA blob from configuration file.
- * Uses the current Node.js process instead of the target binary to avoid issues
- * with cross-platform builds and potentially corrupted downloaded binaries.
- *
- * The blob format is platform-independent, so we can safely use the host Node.js
- * process to generate blobs for any target platform. This approach:
- * 1. Enables cross-platform builds (e.g., building Windows binary on macOS).
- * 2. Avoids issues with downloaded node-smol binaries that may not run on host.
- * 3. Uses the most reliable Node.js binary available (current process).
- *
- * @param {string} configPath - Absolute path to sea-config.json file.
- * @returns Promise resolving to absolute path of generated blob file.
- *
- * @example
- * const blobPath = await buildSeaBlob('dist/sea/sea-config-socket-darwin-arm64.json')
- * // Returns: dist/sea/sea-blob-socket-darwin-arm64.blob
- */
-// c8 ignore start - Requires spawning node binary with experimental SEA config.
-export async function buildSeaBlob(configPath) {
-  const config = JSON.parse(await fs.readFile(configPath, 'utf8'))
-  const blobPath = config.output
-
-  // Generate the blob using the current Node.js process.
-  // We use process.execPath (the current Node) instead of the target binary because:
-  // 1. The blob format is platform-independent.
-  // 2. Downloaded node-smol binaries may have issues running on the host system.
-  // 3. Cross-platform builds wouldn't work (e.g., building Windows binary on macOS).
-  const spawnPromise = spawn(
-    process.execPath,
-    ['--experimental-sea-config', configPath],
-    { stdio: 'inherit' },
-  )
-
-  const result = await spawnPromise
-  if (
-    result &&
-    typeof result === 'object' &&
-    'exitCode' in result &&
-    result.exitCode !== 0
-  ) {
-    throw new Error(`Failed to generate SEA blob: exit code ${result.exitCode}`)
-  }
-
-  return blobPath
-}
-// c8 ignore stop
+// Blob generation is now handled automatically by binject when --sea points to
+// a .json config file. The previous buildSeaBlob() function has been removed
+// because binject can generate the blob using the target binary's Node.js version,
+// which is critical for useCodeCache support (code cache is version-specific).
+//
+// This eliminates the Node.js version mismatch issue where we were using the host
+// Node.js (e.g., v25.5.0) to generate blobs for node-smol targets (e.g., v24.10.0).
+//
+// See injectSeaBlob() below for the config-based blob generation implementation.
 
 // =============================================================================
 // Section 3: Binary Injection.

packages/cli/scripts/test-sea.mjs

@@ -422,9 +422,7 @@ async function runWithToolsMode(platform, toolPaths) {
 
   // Dynamic import Socket modules.
   const { getDefaultLogger } = await import('@socketsecurity/lib/logger')
-  const { buildSeaBlob, injectSeaBlob } = await import(
-    './sea-build-utils/builder.mjs'
-  )
+  const { injectSeaBlob } = await import('./sea-build-utils/builder.mjs')
   const { downloadNodeBinary } = await import(
     './sea-build-utils/downloads.mjs'
   )
@@ -472,12 +470,6 @@ async function runWithToolsMode(platform, toolPaths) {
 
   await fs.writeFile(configPath, JSON.stringify(config, null, 2))
   logger.log(`Wrote SEA config: ${configPath}`)
-
-  // Build SEA blob.
-  logger.log('Generating SEA blob...')
-  await buildSeaBlob(configPath)
-  const blobStats = await fs.stat(blobPath)
-  logger.log(`Blob size: ${(blobStats.size / 1024 / 1024).toFixed(2)} MB`)
   logger.log('')
 
   // Download node-smol binary.
@@ -494,10 +486,18 @@ async function runWithToolsMode(platform, toolPaths) {
   )
   logger.log('')
 
-  // Inject blob into node binary.
-  logger.log('Injecting blob into node binary...')
+  // Inject blob and VFS into binary.
+  // binject will generate the blob automatically using the target binary's
+  // Node.js version when --sea points to a config file.
+  logger.log('Generating SEA blob and injecting into binary...')
   const cacheId = platform
-  await injectSeaBlob(nodeBinary, blobPath, outputPath, cacheId)
+  await injectSeaBlob(nodeBinary, configPath, outputPath, cacheId)
+
+  // Get blob size after it's generated by binject.
+  if (existsSync(blobPath)) {
+    const blobStats = await fs.stat(blobPath)
+    logger.log(`Blob size: ${(blobStats.size / 1024 / 1024).toFixed(2)} MB`)
+  }
 
   // Results.
   const finalStats = await fs.stat(outputPath)