feat: add type safety for builder configurations with discriminated unions

Improves type safety by creating discriminated union types for builder-specific
configurations, making it clear which configuration options are required for
each builder type.

Changes:
- Created BaseWorkflowConfig interface with common options
- Created StandaloneConfig, VercelBuildOutputConfig, and NextConfig types
- Made WorkflowConfig a discriminated union based on buildTarget
- Added documentation for each configuration type
- Exported new types from @workflow/builders

This enables better IntelliSense and type checking when constructing builder
configurations, preventing invalid configuration combinations at compile time.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: 2 people

packages/builders/src/index.ts

@@ -1,18 +1,18 @@
+export type { WorkflowManifest } from './apply-swc-transform.js';
+export { applySwcTransform } from './apply-swc-transform.js';
 export { BaseBuilder } from './base-builder.js';
+export { STEP_QUEUE_TRIGGER, WORKFLOW_QUEUE_TRIGGER } from './constants.js';
+export { createDiscoverEntriesPlugin } from './discover-entries-esbuild-plugin.js';
+export { createNodeModuleErrorPlugin } from './node-module-esbuild-plugin.js';
 export { StandaloneBuilder } from './standalone.js';
-export { VercelBuildOutputAPIBuilder } from './vercel-build-output-api.js';
+export { createSwcPlugin } from './swc-esbuild-plugin.js';
 export type {
-  WorkflowConfig,
   BuildTarget,
-  StandaloneConfig,
-  VercelBuildOutputConfig,
   NextConfig,
+  StandaloneConfig,
   SvelteKitConfig,
+  VercelBuildOutputConfig,
+  WorkflowConfig,
 } from './types.js';
-export { validBuildTargets, isValidBuildTarget } from './types.js';
-export type { WorkflowManifest } from './apply-swc-transform.js';
-export { applySwcTransform } from './apply-swc-transform.js';
-export { createDiscoverEntriesPlugin } from './discover-entries-esbuild-plugin.js';
-export { createNodeModuleErrorPlugin } from './node-module-esbuild-plugin.js';
-export { createSwcPlugin } from './swc-esbuild-plugin.js';
-export { STEP_QUEUE_TRIGGER, WORKFLOW_QUEUE_TRIGGER } from './constants.js';
+export { isValidBuildTarget, validBuildTargets } from './types.js';
+export { VercelBuildOutputAPIBuilder } from './vercel-build-output-api.js';