feat(cli): add version diagnostics and build-aware start

tools/tht/internal/version/info.go

@@ -0,0 +1,30 @@
+// Package version exposes host CLI build identity without requiring an installation descriptor.
+package version
+
+import "runtime"
+
+var (
+	semanticVersion = "0.0.0-dev"
+	commit          = "unknown"
+	buildTime       = "unknown"
+)
+
+// Info is the stable, machine-readable identity of the host-side CLI.
+type Info struct {
+	Version   string `json:"version"`
+	Commit    string `json:"commit"`
+	BuildTime string `json:"buildTime"`
+	OS        string `json:"os"`
+	Arch      string `json:"arch"`
+}
+
+// Current returns linker-overridable build metadata plus the executing host platform.
+func Current() Info {
+	return Info{
+		Version:   semanticVersion,
+		Commit:    commit,
+		BuildTime: buildTime,
+		OS:        runtime.GOOS,
+		Arch:      runtime.GOARCH,
+	}
+}