feat(ipuaro): add function signatures to initial context

- Add full function signatures with parameter types and return types
- Arrow functions now extract returnType in ASTParser
- New formatFunctionSignature() helper in prompts.ts
- Add includeSignatures config option (default: true)
- Support compact format when includeSignatures: false
- 15 new tests, coverage 91.14% branches

packages/ipuaro/src/shared/constants/config.ts

@@ -114,6 +114,7 @@ export const ContextConfigSchema = z.object({
     maxContextUsage: z.number().min(0).max(1).default(0.8),
     autoCompressAt: z.number().min(0).max(1).default(0.8),
     compressionMethod: z.enum(["llm-summary", "truncate"]).default("llm-summary"),
+    includeSignatures: z.boolean().default(true),
 })
 
 /**