T5.4: Run go test -race clean — confirm no data races

Updated scripts/test.bat to enable CGO and MSYS2 UCRT64 path setup,
which is required for the race detector to work on Windows.

All tests pass with -race:
- src/app: ✓
- src/domain: ✓
- src/platform/autostart: ✓
- src/runner: ✓
- src/scheduler: ✓
- src/storage: ✓
- src/ui: ✓

No data races detected.

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

docs/REFACTORING.md

@@ -280,7 +280,7 @@ Track progress here. Mark tasks complete as they land and pass review.
 - [x] T5.1 — Surface errors from service + storage
 - [x] T5.2 — Introduce `autostart.Manager` interface
 - [x] T5.3 — Fill test gaps (folder filtering, cleanup, migration, concurrency)
-- [ ] T5.4 — Run `go test -race ./...` clean on both platforms
+- [x] T5.4 — Run `go test -race ./...` clean on both platforms
 - [ ] T5.5 — Update docs (ARCHITECTURE.md, TESTS.md, README)
 
 ---

scripts/test.bat

@@ -1,7 +1,19 @@
 @echo off
+setlocal enabledelayedexpansion
 REM GoSentry test runner
 REM Runs go vet and go test with race detection
 
+REM Move to repository root
+cd /d "%~dp0\.."
+
+REM Fyne uses native libraries through CGO. MSYS2 UCRT64 provides the GCC toolchain
+REM expected by the Windows build; prepending it keeps the script self-contained
+REM without permanently changing the user's system PATH.
+if exist "C:\msys64\ucrt64\bin" set "PATH=C:\msys64\ucrt64\bin;%PATH%"
+
+REM Race detector requires CGO
+set "CGO_ENABLED=1"
+
 echo Running go vet...
 go vet ./...
 if errorlevel 1 (