Update stale engine test counts to 357 in docs

CONTRIBUTING.md (130), docs/VERSIONS.md (92) and docs/index.md (169) still cited
test-suite sizes from earlier in the project. The suite is 357 tests now, which
matches the README and the actual :engine:test run. Docs only.

Author: jacklau

CONTRIBUTING.md

@@ -28,7 +28,7 @@ Use `./gradlew` (the wrapper) — do not rely on a system Gradle.
 The engine is a normal single Kotlin module. Develop and test it without touching Fabric:
 
 ```bash
-./gradlew :engine:test       # 130 unit tests
+./gradlew :engine:test       # 357 unit tests
 ./gradlew :engine:build
 ```
 

docs/VERSIONS.md

@@ -68,7 +68,7 @@ auto-provisioned by Foojay** on first build.
 > the Java-16 (1.17.1) and Java-8 (1.16.5) variants that shade the engine (JIJ). The engine uses
 > only Kotlin stdlib (`kotlin.collections.ArrayDeque.addFirst` etc.) with no APIs above Java 8,
 > so targeting 8 is behavior-neutral and the Java-8 (major-version-52) bytecode runs on every
-> newer-JVM variant too. `./gradlew :engine:test` stays green at 92 tests.
+> newer-JVM variant too. `./gradlew :engine:test` stays green at 357 tests.
 
 ## Supported versions
 

docs/index.md

@@ -36,7 +36,7 @@ first-class **multi-version** support.
 
     ---
 
-    The engine ships a real unit-test suite (169 tests): lexer, parser, runtime VM,
+    The engine ships a real unit-test suite (357 tests): lexer, parser, runtime VM,
     variables, expressions, actions, pathfinding.
 
 </div>