feat: move buildTypeEdges to src/analysis/type-compat.ts as standalone function

Relocate buildTypeEdges from construction.ts to type-compat.ts per architecture spec.
construction.ts re-exports it for backward compatibility. Add 10 unit tests for
buildTypeEdges covering compatible edges, incompatible edges with mismatches,
unknown schema passthrough, incremental construction, and edge deduplication.

src/index.ts

@@ -1,6 +1,7 @@
 export * from "./error/index.js";
 
 export { FlowGraph, buildTypeEdges, type FlowGraphOptions, type OperationSpec } from "./graph/index.js";
+export { typeCompat, type TypeCompatResult, type TypeMismatch } from "./analysis/type-compat.js";
 export {
   validateSchema,
   validateGraph,