Check queue experiment

.chronus/changes/check-queue-architecture-2026-5-22-12-30-0.md

@@ -0,0 +1,7 @@
+---
+changeKind: feature
+packages:
+  - "@typespec/compiler"
+---
+
+Add worklist-based check queue for type checking declarations, inspired by Rust's obligation forest. Declarations are processed iteratively with deferral and retry, replacing the callback-based `ensureResolved`/`waitingForResolution` mechanism. Circular dependencies are detected via Tarjan's SCC algorithm and reported with clear cycle diagnostics.