feat: add Junie agent integration

Add support for JetBrains Junie AI agent:
- Create .junie/guidelines.md with workflow instructions
- Create .junie/mcp/mcp.json for MCP server configuration
- Add 'junie' to BuiltinRecipes in recipes.go
- Add runJunieRecipe() handler in setup.go
- Add website documentation
- Add integrations/junie/README.md

Usage: bd setup junie

cmd/bd/setup.go

@@ -172,6 +172,9 @@ func runRecipe(name string) {
 	case "cursor":
 		runCursorRecipe()
 		return
+	case "junie":
+		runJunieRecipe()
+		return
 	}
 
 	// For all other recipes (built-in or user), use generic file-based install
@@ -296,6 +299,18 @@ func runAiderRecipe() {
 	setup.InstallAider()
 }
 
+func runJunieRecipe() {
+	if setupCheck {
+		setup.CheckJunie()
+		return
+	}
+	if setupRemove {
+		setup.RemoveJunie()
+		return
+	}
+	setup.InstallJunie()
+}
+
 func findBeadsDir() string {
 	// Check for .beads in current directory
 	if info, err := os.Stat(".beads"); err == nil && info.IsDir() {