chore: remove dead code (packages, functions, types, constants)

Remove 5 unused packages (daemon, preview, proxy, workflow) and dead
symbols across 7 files: orchestrator workflow engine, skills Target type
and Update(), LSP config generation, installer SetupPrompt(), unexported
desktop options, and version License/Prerelease. Total: -1453 lines.

internal/version/version.go

@@ -4,15 +4,8 @@ const (
 	Name    = "muyue"
 	Version = "0.2.1"
 	Author  = "La Légion de Muyue"
-	License = "MIT"
 )
 
-var Prerelease string
-
 func FullVersion() string {
-	v := Name + " v" + Version
-	if Prerelease != "" {
-		v += "-" + Prerelease
-	}
-	return v
+	return Name + " v" + Version
 }

internal/version/version_test.go

@@ -15,28 +15,6 @@ func TestFullVersion(t *testing.T) {
 	}
 }
 
-func TestFullVersionWithPrerelease(t *testing.T) {
-	original := Prerelease
-	Prerelease = "beta.1"
-	defer func() { Prerelease = original }()
-
-	v := FullVersion()
-	if !strings.Contains(v, "beta.1") {
-		t.Errorf("FullVersion should contain prerelease suffix, got %s", v)
-	}
-}
-
-func TestFullVersionWithoutPrerelease(t *testing.T) {
-	original := Prerelease
-	Prerelease = ""
-	defer func() { Prerelease = original }()
-
-	v := FullVersion()
-	if strings.Contains(v, "-") {
-		t.Errorf("FullVersion should not contain prerelease suffix, got %s", v)
-	}
-}
-
 func TestConstants(t *testing.T) {
 	if Name == "" {
 		t.Error("Name should not be empty")
@@ -47,7 +25,4 @@ func TestConstants(t *testing.T) {
 	if Author == "" {
 		t.Error("Author should not be empty")
 	}
-	if License == "" {
-		t.Error("License should not be empty")
-	}
 }