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_openbsd.go

@@ -0,0 +1,14 @@
+package browser
+
+import (
+	"errors"
+	"os/exec"
+)
+
+func openBrowser(url string) error {
+	err := runCmd("xdg-open", url)
+	if e, ok := err.(*exec.Error); ok && e.Err == exec.ErrNotFound {
+		return errors.New("xdg-open: command not found - install xdg-utils from ports(8)")
+	}
+	return err
+}