Provide agent guidance on JSG_TRY vs. js.tryCatch

docs/reference/detail/legacy-module-registry.md

@@ -216,7 +216,7 @@ Flow:
 9. On not-found: retry with absolute path for `node:`/`cloudflare:` prefixed specifiers.
 10. Final fallback: throw `"No such module"` error.
 
-Errors are handled via `js.tryCatch`: exceptions are caught, and
+Errors are handled via `JSG_TRY/JSG_CATCH`: exceptions are caught, and
 `js.v8Isolate->ThrowException()` is called to schedule them on the isolate
 (V8 requires exceptions to be scheduled, not thrown as C++ exceptions, during
 resolve callbacks).

src/workerd/jsg/AGENTS.md

@@ -62,6 +62,14 @@ class MyType: public jsg::Object {
 - `TypeHandler<T>&` as trailing param gives manual conversion access
 - Compat flags param on `JSG_RESOURCE_TYPE` gates members conditionally
 
+## Errors
+
+Use `JSG_TRY(js) { ... } JSG_CATCH(exception) { ... }` to catch JS exceptions in
+C++ code. The `js` is a `jsg::Lock&` parameter. The `exception` is a `jsg::Value`
+containing the JS exception that was thrown.
+
+The legacy `js.tryCatch(fn)` is deprecated and will be eventually removed.
+
 ## ANTI-PATTERNS
 
 - **NEVER** opaque-wrap `V8Ref<T>` — use handle directly