feat(ingestion): implement brain_ingest_raw MCP tool

Wraps pipeline.RunRaw directly. Same dry-run semantics as the HTTP
/ingest-raw endpoint. Test exercises a single concept page; asserts
returned path and that no file is written under dry_run.

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

ingestion/internal/mcp/handlers_test.go

@@ -94,3 +94,36 @@ func TestBrainWriteAcceptsDoubleDotInName(t *testing.T) {
 	_, err := os.Stat(filepath.Join(brainDir, "knowledge", "notes..draft.md"))
 	require.NoError(t, err, "filename with embedded .. should be allowed")
 }
+
+func TestBrainIngestRawDryRun(t *testing.T) {
+	brainDir := t.TempDir()
+	require.NoError(t, os.MkdirAll(filepath.Join(brainDir, "wiki", "concepts"), 0o755))
+	srv := mcp.NewServer(brainDir, nil, nil)
+
+	resp := toolCall(t, srv, "brain_ingest_raw", map[string]any{
+		"source":  "test-source",
+		"dry_run": true,
+		"pages": []map[string]any{
+			{
+				"title":   "Test Concept",
+				"type":    "concept",
+				"content": "## Definition\nA test concept.",
+			},
+		},
+	})
+	require.Nil(t, resp["error"])
+	result := resp["result"].(map[string]any)
+	content := result["content"].([]any)
+	text := content[0].(map[string]any)["text"].(string)
+
+	var parsed struct {
+		Pages []string `json:"pages"`
+	}
+	require.NoError(t, json.Unmarshal([]byte(text), &parsed))
+	require.NotEmpty(t, parsed.Pages, "expected at least one page path")
+	assert.Contains(t, parsed.Pages[0], "wiki/concepts/test-concept.md")
+
+	// dry_run: no file should exist
+	_, err := os.Stat(filepath.Join(brainDir, "wiki", "concepts", "test-concept.md"))
+	assert.True(t, os.IsNotExist(err))
+}