Switch remote deploy to vendored source builds

Move remote deployment to a vendored source bundle built on the target host via Docker so redeploys no longer require local cross-compilation or host Go installation.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

vendor/github.com/pkg/browser/browser_unsupported.go

@@ -0,0 +1,12 @@
+// +build !linux,!windows,!darwin,!openbsd,!freebsd,!netbsd
+
+package browser
+
+import (
+	"fmt"
+	"runtime"
+)
+
+func openBrowser(url string) error {
+	return fmt.Errorf("openBrowser: unsupported operating system: %v", runtime.GOOS)
+}