feat(ingestion): add MCP server skeleton with tools/list

Adds an MCP HTTP handler under ingestion/internal/mcp. Implements
initialize, tools/list, and the JSON-RPC notification skip from prior
work. Tool dispatch is stubbed (returns unknown-tool error) and will be
filled in by subsequent tasks.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ingestion/internal/mcp/server_test.go

@@ -0,0 +1,91 @@
+package mcp_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/mathiasbq/hyperguild/ingestion/internal/mcp"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func body(t *testing.T, v any) *bytes.Buffer {
+	t.Helper()
+	b, err := json.Marshal(v)
+	require.NoError(t, err)
+	return bytes.NewBuffer(b)
+}
+
+func TestServerInitialize(t *testing.T) {
+	srv := mcp.NewServer(t.TempDir(), nil, nil)
+
+	req := httptest.NewRequest(http.MethodPost, "/mcp", body(t, map[string]any{
+		"jsonrpc": "2.0", "id": 1, "method": "initialize",
+		"params": map[string]any{},
+	}))
+	rr := httptest.NewRecorder()
+	srv.ServeHTTP(rr, req)
+
+	assert.Equal(t, http.StatusOK, rr.Code)
+	var resp map[string]any
+	require.NoError(t, json.Unmarshal(rr.Body.Bytes(), &resp))
+	result := resp["result"].(map[string]any)
+	assert.Equal(t, "2024-11-05", result["protocolVersion"])
+}
+
+func TestServerToolsList(t *testing.T) {
+	srv := mcp.NewServer(t.TempDir(), nil, nil)
+
+	req := httptest.NewRequest(http.MethodPost, "/mcp", body(t, map[string]any{
+		"jsonrpc": "2.0", "id": 2, "method": "tools/list",
+	}))
+	rr := httptest.NewRecorder()
+	srv.ServeHTTP(rr, req)
+
+	assert.Equal(t, http.StatusOK, rr.Code)
+	var resp map[string]any
+	require.NoError(t, json.Unmarshal(rr.Body.Bytes(), &resp))
+	tools := resp["result"].(map[string]any)["tools"].([]any)
+	names := make([]string, 0, len(tools))
+	for _, t := range tools {
+		names = append(names, t.(map[string]any)["name"].(string))
+	}
+	assert.ElementsMatch(t, []string{
+		"brain_query", "brain_write", "brain_ingest_raw", "brain_ingest", "session_log",
+	}, names)
+}
+
+func TestServerNotificationGetsNoBody(t *testing.T) {
+	srv := mcp.NewServer(t.TempDir(), nil, nil)
+
+	req := httptest.NewRequest(http.MethodPost, "/mcp", body(t, map[string]any{
+		"jsonrpc": "2.0", "method": "notifications/initialized",
+	}))
+	rr := httptest.NewRecorder()
+	srv.ServeHTTP(rr, req)
+
+	assert.Equal(t, http.StatusOK, rr.Code)
+	assert.Empty(t, strings.TrimSpace(rr.Body.String()))
+}
+
+func TestServerUnknownMethodReturnsError(t *testing.T) {
+	srv := mcp.NewServer(t.TempDir(), nil, nil)
+
+	req := httptest.NewRequest(http.MethodPost, "/mcp", body(t, map[string]any{
+		"jsonrpc": "2.0", "id": 3, "method": "unknown/method",
+	}))
+	rr := httptest.NewRecorder()
+	srv.ServeHTTP(rr, req)
+
+	assert.Equal(t, http.StatusOK, rr.Code)
+	var resp map[string]any
+	require.NoError(t, json.Unmarshal(rr.Body.Bytes(), &resp))
+	require.NotNil(t, resp["error"])
+	errObj := resp["error"].(map[string]any)
+	assert.Equal(t, float64(-32601), errObj["code"])
+	assert.Contains(t, errObj["message"].(string), "unknown/method")
+}