CFG_VER is always a concrete version: dev builds stamp v0.0.0, never "dev"

SPEC.md

@@ -159,7 +159,7 @@ override file values. A missing file is fine; a malformed one is fatal.
 | `UPDATE_REPO` | `https://git.rambossek.at/PUBLIC/gpu-turnstile` | repository to check for releases |
 | `UPDATE_ASSET` | `gpu-turnstile.exe` | release asset to download |
 | `APP_VER` | `stable` | version to run: `dev` disables updates, `stable` tracks the latest release, or an exact `vX.Y.Z` pin (up- or downgraded to) |
-| `CFG_VER` | _(installer-managed)_ | config format reference written by `--install-service`; missing = the file is replaced with a fresh sample (backup `.bak`) |
+| `CFG_VER` | _(installer-managed)_ | config format reference written by `--install-service` (always a concrete `vX.Y.Z`; a dev build stamps `v0.0.0`); missing = the file is replaced with a fresh sample (backup `.bak`) |
 
 Startup fails fast on unparsable values and when neither consumer URL is
 set. Enabled upstreams are probed once at start (`/api/version`,

internal/config/sample.go

@@ -59,8 +59,15 @@ func sampleEntries(logFile string) []sampleEntry {
 // (a Windows service has no console). CFG_VER records the version that
 // wrote the file so later installs can upgrade it.
 func SampleEnv(version, logFile string) string {
+	// CFG_VER is always a concrete vX.Y.Z — never "dev". A dev build
+	// stamps v0.0.0, which sorts older than any release, so the next
+	// release install upgrades the file and stamps a proper version.
+	cfgVer := version
+	if cfgVer == "" || cfgVer == "dev" {
+		cfgVer = "v0.0.0"
+	}
 	var b strings.Builder
-	fmt.Fprintf(&b, "CFG_VER=%s\n", version)
+	fmt.Fprintf(&b, "CFG_VER=%s\n", cfgVer)
 	b.WriteString("# Config format reference, written by the installer — do not edit.\n")
 	b.WriteString("# The installer uses it to append newly added settings on updates.\n\n")
 	b.WriteString("# gpu-turnstile configuration\n")

internal/config/sample_test.go

@@ -122,6 +122,19 @@ func TestSyncSampleAppendsMissingAppVer(t *testing.T) {
 	}
 }
 
+func TestSampleEnvDevStampsConcreteVersion(t *testing.T) {
+	// A dev build must never write CFG_VER=dev: it stamps v0.0.0, and the
+	// next release install upgrades the file to a proper version.
+	dev := SampleEnv("dev", sampleLogPath)
+	if !strings.HasPrefix(dev, "CFG_VER=v0.0.0\n") {
+		t.Errorf("dev sample first line: %q", strings.SplitN(dev, "\n", 2)[0])
+	}
+	out, changed := SyncSample(dev, "v0.1.7", sampleLogPath)
+	if !changed || !strings.HasPrefix(out, "CFG_VER=v0.1.7\n") {
+		t.Errorf("dev-stamped file was not upgraded to v0.1.7 (changed=%v)", changed)
+	}
+}
+
 func TestCompareVersions(t *testing.T) {
 	cases := []struct {
 		a, b string