feat(cli): trigger self-install rune-mcp on first 'rune mcp-server' invocation

Author: esifea

cmd/rune/mcpserver.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"os"
+	"time"
 
 	"github.com/CryptoLabInc/rune-cli/internal/bootstrap"
 )
@@ -15,5 +17,59 @@ func runMCPServer(ctx context.Context, args []string, stderr io.Writer) int {
 		return 1
 	}
 
+	// Fresh `claude plugin install rune` try to spawn MCP server via
+	// "${CLAUDE_PLUGIN_ROOT}/bin/rune mcp-server" which does not exist yet.
+	// Self-install rune-mcp itself in this case.
+	if _, statErr := os.Stat(paths.RuneMCPBinary); statErr != nil {
+		fmt.Fprintln(stderr, "rune: rune-mcp not installed yet; fetching before launch...")
+		manifest := manifestURL
+		if env := os.Getenv("RUNE_MANIFEST"); env != "" {
+			manifest = env
+		}
+
+		// Concurrency-safe install
+		_, instErr := bootstrap.Install(ctx, bootstrap.InstallOptions{
+			ManifestURL: manifest,
+			Target:      []string{bootstrap.StepRuneMCP},
+			Log: func(format string, a ...any) {
+				fmt.Fprintf(stderr, format+"\n", a...)
+			},
+		})
+		if instErr != nil {
+			// Sessions which do not invoke install wait here
+			if !waitForFile(ctx, paths.RuneMCPBinary, bootstrap.InstallLockTimeout) {
+				fmt.Fprintf(stderr, "rune: failed to install rune-mcp: %v\n", instErr)
+				return 1
+			}
+
+			fmt.Fprintln(stderr, "rune: rune-mcp installed by a concurrent session")
+		}
+	}
+
 	return execInstalledBinary(ctx, paths.RuneBin, "rune-mcp", args, nil, stderr)
 }
+
+func waitForFile(ctx context.Context, path string, timeout time.Duration) bool {
+	if _, err := os.Stat(path); err == nil {
+		return true
+	}
+
+	deadline := time.NewTimer(timeout)
+	defer deadline.Stop()
+
+	tick := time.NewTicker(300 * time.Millisecond)
+	defer tick.Stop()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return false
+		case <-deadline.C:
+			return false
+		case <-tick.C:
+			if _, err := os.Stat(path); err == nil {
+				return true
+			}
+		}
+	}
+}