add targets field to filter tools per agent harness (pi/claude/all)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/servers/mcp-tool-server.ts

@@ -32,6 +32,7 @@ type ToolMeta = {
   label: string;
   description: string;
   inputs: Record<string, ToolParam>;
+  targets?: string;
 };
 
 type DiscoveredTool = {
@@ -138,6 +139,7 @@ function discoverTools(dirs: string[]): DiscoveredTool[] {
       const { meta } = parseFrontmatter(content);
 
       if (!meta.name || !meta.description) continue;
+      if ((meta.targets as string ?? 'all') === 'pi') continue;
       if (seen.has(meta.name)) continue;
       seen.add(meta.name);