feat: add brain_query and brain_write MCP tools

Adds the brain skill that proxies HTTP calls to the ingestion server,
exposing brain_query (/query) and brain_write (/write) as MCP tools.

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

internal/skills/brain/handlers_test.go

@@ -0,0 +1,61 @@
+// internal/skills/brain/handlers_test.go
+package brain_test
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/mathiasbq/supervisor/internal/skills/brain"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestHandle_BrainQuery_CallsIngestServer(t *testing.T) {
+	called := false
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		assert.Equal(t, "/query", r.URL.Path)
+		called = true
+		json.NewEncoder(w).Encode(map[string]any{
+			"results": []map[string]any{
+				{"path": "wiki/concepts/tdd.md", "title": "TDD", "excerpt": "Test-driven development.", "score": 3},
+			},
+		})
+	}))
+	defer srv.Close()
+
+	s := brain.New(brain.Config{IngestBaseURL: srv.URL})
+	args, _ := json.Marshal(map[string]string{"query": "test driven development"})
+	out, err := s.Handle(context.Background(), "brain_query", args)
+	require.NoError(t, err)
+	assert.True(t, called)
+
+	var result map[string]any
+	require.NoError(t, json.Unmarshal(out, &result))
+	results := result["results"].([]any)
+	assert.Len(t, results, 1)
+}
+
+func TestHandle_BrainWrite_CallsIngestServer(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		assert.Equal(t, "/write", r.URL.Path)
+		json.NewEncoder(w).Encode(map[string]string{"path": "raw/test.md"})
+	}))
+	defer srv.Close()
+
+	s := brain.New(brain.Config{IngestBaseURL: srv.URL})
+	args, _ := json.Marshal(map[string]string{"content": "# Test\n\nSome learning.", "type": "concept"})
+	out, err := s.Handle(context.Background(), "brain_write", args)
+	require.NoError(t, err)
+	var result map[string]string
+	require.NoError(t, json.Unmarshal(out, &result))
+	assert.Equal(t, "raw/test.md", result["path"])
+}
+
+func TestHandle_UnknownTool_ReturnsError(t *testing.T) {
+	s := brain.New(brain.Config{IngestBaseURL: "http://localhost:3300"})
+	_, err := s.Handle(context.Background(), "brain_unknown", nil)
+	assert.Error(t, err)
+}