feat: add @automaker/model-resolver package

- Extract model string resolution logic
- Map model aliases to full model strings (haiku -> claude-haiku-4-5)
- Handle multiple model sources with priority
- Re-export model constants from @automaker/types

Provides centralized model resolution for Claude models.
Simplifies model handling across server and UI.

Dependencies: @automaker/types

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

libs/model-resolver/src/index.ts

@@ -0,0 +1,13 @@
+/**
+ * @automaker/model-resolver
+ * Model resolution utilities for AutoMaker
+ */
+
+// Re-export constants from types
+export { CLAUDE_MODEL_MAP, DEFAULT_MODELS, type ModelAlias } from '@automaker/types';
+
+// Export resolver functions
+export {
+  resolveModelString,
+  getEffectiveModel,
+} from './resolver';