chore: inject the version into main instead of a module path

The `-X` target carried the full module path in both the Makefile and
.goreleaser.yaml, so any change to the module path silently turned the
injection into a no-op and shipped a binary reporting "dev". Target
`main.version` instead, which no longer names the module, and fail
`make checks` when the injection stops taking effect.

Assisted-by: Codet:GPT-5.1-Codex

main.go

@@ -9,9 +9,14 @@ import (
 	"syscall"
 
 	"gitea.com/gitea/runner/internal/app/cmd"
+	"gitea.com/gitea/runner/internal/pkg/ver"
 )
 
+// version is injected at build time with `-ldflags "-X main.version=v1.2.3"`.
+var version = "dev"
+
 func main() {
+	ver.SetVersion(version)
 	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
 	defer stop()
 	// run the command