feat: align MCP retrieval contract with ra-h

- add external retrieval and confirmation-gated writeback tools across MCP surfaces
- port direct-search-first retrieval support and supporting ranking/query updates
- update MCP docs and skills to treat agent memory files as optional reinforcement

Generated with Claude Code

app/api/retrieval/query-context/route.ts

@@ -0,0 +1,35 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { retrieveQueryContext } from '@/services/retrieval/queryContext';
+
+export const runtime = 'nodejs';
+
+export async function POST(request: NextRequest) {
+  try {
+    const body = await request.json();
+    const query = typeof body.query === 'string' ? body.query : '';
+
+    if (!query.trim()) {
+      return NextResponse.json({
+        success: false,
+        error: 'Missing required field: query',
+      }, { status: 400 });
+    }
+
+    const result = await retrieveQueryContext({
+      query,
+      focused_node_id: typeof body.focused_node_id === 'number' ? body.focused_node_id : null,
+      active_context_id: typeof body.active_context_id === 'number' ? body.active_context_id : null,
+      limit: typeof body.limit === 'number' ? body.limit : undefined,
+    });
+
+    return NextResponse.json({
+      success: true,
+      data: result,
+    });
+  } catch (error) {
+    return NextResponse.json({
+      success: false,
+      error: error instanceof Error ? error.message : 'Failed to retrieve query context',
+    }, { status: 500 });
+  }
+}