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_linux.go

@@ -0,0 +1,21 @@
+package browser
+
+import (
+	"os/exec"
+	"strings"
+)
+
+func openBrowser(url string) error {
+	providers := []string{"xdg-open", "x-www-browser", "www-browser"}
+
+	// There are multiple possible providers to open a browser on linux
+	// One of them is xdg-open, another is x-www-browser, then there's www-browser, etc.
+	// Look for one that exists and run it
+	for _, provider := range providers {
+		if _, err := exec.LookPath(provider); err == nil {
+			return runCmd(provider, url)
+		}
+	}
+
+	return &exec.Error{Name: strings.Join(providers, ","), Err: exec.ErrNotFound}
+}