fix(skillmgr): use built sin-websearch binary from SIN_SKILLS_DIR

The registry used the bare command name 'sin-websearch', which only works
if the user manually puts the binary on PATH. Now the registry checks
SIN_SKILLS_DIR/web_search_bundle/sin-websearch first and falls back to
PATH. The skill manager also builds the binary explicitly into the repo
root with -o sin-websearch so the registry can find it.

Adds tests for both the local-binary and PATH-fallback cases.

Author: Delqhi

cmd/sin-code/internal/mcpclient/registry.go

@@ -26,9 +26,28 @@ func DefaultServers() []ServerConfig {
 		}
 		return cfg
 	}
+	// goNative returns a ServerConfig for a Go-native skill. It prefers the
+	// binary built inside SIN_SKILLS_DIR/<repo>/sin-websearch so that skillmgr
+	// can install and run the skill without requiring the user to put the binary
+	// on PATH. Falls back to the binary name on PATH if no local checkout exists.
+	goNative := func(repo, binary string, args ...string) ServerConfig {
+		name := shortName(repo)
+		cfg := ServerConfig{Name: name, Transport: "stdio", Args: args}
+		if skillsDir != "" {
+			localBin := filepath.Join(skillsDir, repo, binary)
+			if _, err := os.Stat(localBin); err == nil {
+				cfg.Command = localBin
+			} else {
+				cfg.Command = binary
+			}
+		} else {
+			cfg.Command = binary
+		}
+		return cfg
+	}
 	return []ServerConfig{
 		// web_search_bundle is the Go-native successor to SIN-Code-Websearch-Skill.
-		{Name: "websearch", Transport: "stdio", Command: "sin-websearch", Args: []string{"serve"}},
+		goNative("web_search_bundle", "sin-websearch", "serve"),
 		py("SIN-Code-Scheduler-Skill"),
 		py("SIN-Code-Goal-Mode-Skill"),
 		py("SIN-Code-Grill-Me-Skill"),

cmd/sin-code/internal/mcpclient/registry_test.go

@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: MIT
+// Purpose: tests for the built-in ecosystem registry in mcpclient.
+package mcpclient
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestDefaultServersWebsearchUsesLocalBinaryWhenPresent(t *testing.T) {
+	dir := t.TempDir()
+	bin := filepath.Join(dir, "web_search_bundle", "sin-websearch")
+	if err := os.MkdirAll(filepath.Dir(bin), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(bin, []byte("#!/bin/sh\necho fake"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+
+	t.Setenv("SIN_SKILLS_DIR", dir)
+	for _, s := range DefaultServers() {
+		if s.Name != "websearch" {
+			continue
+		}
+		if s.Command != bin {
+			t.Fatalf("websearch command should use local binary %q, got %q", bin, s.Command)
+		}
+		if len(s.Args) != 1 || s.Args[0] != "serve" {
+			t.Fatalf("websearch args should be [serve], got %v", s.Args)
+		}
+		return
+	}
+	t.Fatal("websearch server not found in DefaultServers")
+}
+
+func TestDefaultServersWebsearchFallsBackToPathBinary(t *testing.T) {
+	t.Setenv("SIN_SKILLS_DIR", "")
+	for _, s := range DefaultServers() {
+		if s.Name != "websearch" {
+			continue
+		}
+		if s.Command != "sin-websearch" {
+			t.Fatalf("websearch command should fall back to %q, got %q", "sin-websearch", s.Command)
+		}
+		return
+	}
+	t.Fatal("websearch server not found in DefaultServers")
+}

cmd/sin-code/internal/skillmgr/manager.go

@@ -125,8 +125,9 @@ func verifyEntrypoint(ctx context.Context, dir string) (bool, string) {
 		return true, "node entrypoint (package.json)"
 	}
 	if _, err := os.Stat(filepath.Join(dir, "go.mod")); err == nil {
-		// Go-native skill: verify it compiles.
-		cmd := exec.CommandContext(ctx, "go", "build", "./cmd/sin-websearch")
+		// Go-native skill: build the binary into the repo root so the MCP
+		// registry can use the full path (SIN_SKILLS_DIR/<repo>/<binary>).
+		cmd := exec.CommandContext(ctx, "go", "build", "-o", "sin-websearch", "./cmd/sin-websearch")
 		cmd.Dir = dir
 		if _, err := cmd.CombinedOutput(); err != nil {
 			return false, fmt.Sprintf("go entrypoint exists but build failed: %v", err)