Document version 3.0.0 changes and migration

README.md

@@ -12,6 +12,8 @@ four main motivating features:
 
 ## Getting Started
 
+See the [changelog](CHANGELOG.md) for version 3.0.0 changes and migration notes.
+
 Install the package via nimble:
 
 ```bash
@@ -588,12 +590,13 @@ file system operations that might fail and cause cascading errors.
 
 ## Testing
 
-Run `nimble test` for all unit, regression, and ThreadSanitizer ownership tests.
+Run `nimble test` for all enabled unit, regression, and ThreadSanitizer ownership tests.
 It runs every suite even when an earlier suite fails. For focused debugging,
 use `nimble testUnit`, `nimble testRegression`, or `nimble testThreadSafety`.
-The regression tests currently expose known defects and are expected to fail
-until those defects are fixed. See [tests/README.md](tests/README.md) for commands,
-requirements, and coverage limitations.
+Two scenarios that expose a known Nim allocator race are temporarily skipped
+by default. Enable them with `NSL_TEST_RUNTIME_ALLOCATOR=1 nimble testThreadSafety`.
+See [tests/README.md](tests/README.md) for commands, requirements, and coverage
+limitations.
 
 [log4j]: https://logging.apache.org/log4j/2.x/
 [logback]: https://logback.qos.ch/