feat: Linux desktop companion app with auto-install, Gateway lifecycle, and Control UI window (#106352)

* feat(linux): add Tauri desktop companion app and openclaw dashboard --json

* test(dashboard): assemble fake token fixture to satisfy secret scanners

* test(dashboard): avoid secret-scanner-shaped mock factory line

* fix(linux): actionable error when installed CLI predates dashboard --json

* docs: regenerate docs map for linux platform heading change

apps/linux/src-tauri/build.rs

@@ -0,0 +1,3 @@
+fn main() {
+    tauri_build::build();
+}