feat: migrate from NPM_CONFIG_PRODUCTION to NPM_CONFIG_OMIT

Replace the deprecated NPM_CONFIG_PRODUCTION environment variable with
NPM_CONFIG_OMIT=dev,optional for exact parity with previous behavior.

Changes:
- Remove --omit=dev flag from npm prune command
- Set NPM_CONFIG_OMIT=dev,optional in prune step instead of NPM_CONFIG_PRODUCTION=true
- This approach uses environment variables as recommended

The new approach:
- Omits devDependencies (via "dev")
- Omits optionalDependencies (via "optional")
- Maintains NODE_ENV=production for lifecycle scripts

This provides exact behavioral parity with the old NPM_CONFIG_PRODUCTION=true
approach while using the modern npm configuration method.

Author: claude

core/providers/node/node.go

@@ -243,7 +243,7 @@ func (p *NodeProvider) shouldPrune(ctx *generate.GenerateContext) bool {
 
 func (p *NodeProvider) PruneNodeDeps(ctx *generate.GenerateContext, prune *generate.CommandStepBuilder) {
 	ctx.Logger.LogInfo("Pruning node dependencies")
-	prune.Variables["NPM_CONFIG_PRODUCTION"] = "true"
+	prune.Variables["NPM_CONFIG_OMIT"] = "dev,optional"
 	prune.Secrets = []string{}
 	p.packageManager.PruneDeps(ctx, prune)
 }

core/providers/node/package_manager.go

@@ -145,7 +145,7 @@ func (p PackageManager) PruneDeps(ctx *generate.GenerateContext, prune *generate
 
 	switch p {
 	case PackageManagerNpm:
-		prune.AddCommand(plan.NewExecCommand("npm prune --omit=dev --ignore-scripts"))
+		prune.AddCommand(plan.NewExecCommand("npm prune --ignore-scripts"))
 	case PackageManagerPnpm:
 		p.prunePnpm(ctx, prune)
 	case PackageManagerBun: