T0.1: Add test scripts and documentation

Add scripts/test.sh and scripts/test.bat to run go vet and go test -race.
Update docs/TESTS.md with test script usage and reorganized manual test commands.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

scripts/test.bat

@@ -0,0 +1,23 @@
+@echo off
+REM GoSentry test runner
+REM Runs go vet and go test with race detection
+
+echo Running go vet...
+go vet ./...
+if errorlevel 1 (
+    echo.
+    echo ✗ go vet failed
+    exit /b 1
+)
+
+echo.
+echo Running go test with race detection...
+go test -race ./...
+if errorlevel 1 (
+    echo.
+    echo ✗ go test failed
+    exit /b 1
+)
+
+echo.
+echo ✓ All tests passed