fix(mcp): implement tools.discovery handler returning flat tool catalog

The tools.discovery tool was declared in the catalog (line 1300) but no
tools/call dispatch branch existed for it — every call fell through to
'Unknown tool: tools.discovery'. Functionality was reachable only via
the parallel GET /api/mcp endpoint, which the JSON-RPC-only MCP clients
in n8n couldn't use.

Add a real handler that returns the same `tools` array as tools/list,
wrapped in the standard JSON-RPC content envelope. Mirrors GET /api/mcp
for JSON-RPC-only clients.

Also add a Vitest case that asserts the catalog shape (array of tools,
each with name+description+inputSchema, and tools.discovery in the list).

Deployment note: this fix is in source; the live apphub.co.za server
runs a built bundle and will keep returning 'Unknown tool' until rebuilt.

Co-authored-by: Orca <help@stably.ai>

src/app/api/mcp/route.test.ts

@@ -301,6 +301,28 @@ describe("POST /api/mcp", () => {
     expect(body.error.message).toMatch(/Unknown tool/);
   });
 
+  it("tools/call tools.discovery returns the flat tool catalog (JSON-RPC form of GET /api/mcp)", async () => {
+    const res = await POST(
+      mcpRequest({
+        method: "tools/call",
+        id: 8,
+        params: { name: "tools.discovery", arguments: {} },
+      })
+    );
+    expect(res.status).toBe(200);
+    const body = await res.json();
+    const payload = JSON.parse(body.result.content[0].text);
+    expect(Array.isArray(payload.tools)).toBe(true);
+    expect(payload.tools.length).toBeGreaterThan(60);
+    // Every entry has name + description + inputSchema
+    for (const t of payload.tools) {
+      expect(typeof t.name).toBe("string");
+      expect(typeof t.description).toBe("string");
+      expect(t.inputSchema).toBeDefined();
+    }
+    expect(payload.tools.map((t: { name: string }) => t.name)).toContain("tools.discovery");
+  });
+
   it("tools/call quotes.create_from_email delegates to the service with the full payload", async () => {
     createQuoteFromEmail.mockResolvedValueOnce({
       quote: { id: "q1" },

src/app/api/mcp/route.ts

@@ -2489,6 +2489,15 @@ export async function POST(req: NextRequest) {
         return jsonRpcOk(body.id, { deleted: args.id });
       }
 
+      // tools.discovery — flat tool catalog (no JSON-RPC envelope inside
+      // the text payload). Mirrors `GET /api/mcp` for clients that can
+      // only build a JSON-RPC request. Returns the same `tools` array as
+      // `tools/list` — handy when an agent wants a self-describing
+      // summary without paying the schema-drift tax of two surfaces.
+      if (toolName === "tools.discovery") {
+        return jsonRpcOk(body.id, { tools });
+      }
+
       throw new Error(`Unknown tool: ${toolName}`);
     }