refactor: unify into single muyue binary with embedded desktop mode

- Merge muyue + muyue-desktop into one binary (13MB)
- `muyue` starts TUI, `muyue desktop` launches web UI in browser
- Move frontend from cmd/muyue-desktop/frontend/ to web/ (standard Go layout)
- Add web/embed.go with //go:embed all:dist for frontend assets
- Add internal/desktop/ package (server, browser open, SPA routing, signals)
- Split internal/api/api.go into server.go + handlers.go
- Add internal/desktop/desktop.go with SPA fallback and --port/--no-open flags
- Clean package.json: remove unused @xterm/xterm, switch to ESM
- Fix vite.config.js proxy to use port 8095 for dev mode
- Add Makefile targets: frontend, desktop, dev-desktop
- Update all CI workflows: single binary build, web/ paths
- Remove cmd/muyue-desktop/ entirely

💘 Generated with Crush

Assisted-by: GLM-5.1 via Crush <crush@charm.land>

cmd/muyue/main.go

@@ -7,6 +7,7 @@ import (
 
 	tea "github.com/charmbracelet/bubbletea"
 	"github.com/muyue/muyue/internal/config"
+	"github.com/muyue/muyue/internal/desktop"
 	"github.com/muyue/muyue/internal/installer"
 	"github.com/muyue/muyue/internal/lsp"
 	"github.com/muyue/muyue/internal/mcp"
@@ -53,6 +54,8 @@ func handleCommand(args []string) {
 		runLSP(args[1:])
 	case "mcp":
 		runMCP(args[1:])
+	case "desktop":
+		runDesktop(args[1:])
 	case "skills":
 		runSkills(args[1:])
 	case "help", "-h", "--help":
@@ -79,6 +82,7 @@ Commands:
   setup              Run first-time setup wizard
   config             Show current configuration
   doctor             Check that everything is properly configured
+  desktop            Launch desktop web UI (opens browser)
   lsp [scan|install] Scan or install LSP servers
   mcp [config|scan]  Configure MCP servers for Crush and Claude Code
   skills [list|generate|deploy|init|delete] Manage AI coding skills
@@ -118,6 +122,14 @@ func runTUI() {
 	}
 }
 
+func runDesktop(args []string) {
+	cfg := loadOrSetupConfig()
+	if err := desktop.Run(cfg, args); err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		os.Exit(1)
+	}
+}
+
 func loadOrSetupConfig() *config.MuyueConfig {
 	if !config.Exists() {
 		fmt.Println("First time setup detected!")