feat(mcp): add drawing_create_text tool with Web UI compatible SVG assembly

The Web UI re-parses drawing SVG into its own element model instead of
rendering it raw, which makes hand-assembled SVG error-prone for LLM
callers. The new tool assembles the SVG server-side, mirroring what the
Web UI itself serializes for text drawings:

- XML-escaped text content, validated color (#RGB/#RGBA/#RRGGBB/
  #RRGGBBAA) and font family (attribute-safe charset)
- multi-line support: literal newlines render as stacked lines in the
  Web UI (tspan split), width/height computed from the longest line
- pt-aware sizing: the Web UI renders font-size in pt (1pt = 4/3 px),
  so width uses a 0.8/char factor for monospace (1.0 proportional) and
  line height 1.9 x font_size, instead of the px-based 0.62 estimate
- ET.fromstring pre-check so bad input fails loudly instead of hitting
  the controller's silent drop of unparseable 500+ char SVG
- computed width/height/line_height returned for label layout

Also correct the raw drawing_create docstring: root width/height are
required (the parser reads them for the selection box), x/y on rect are
ignored, <g> is unsupported, <path> is re-interpreted as a freehand
curve, and the old examples lacked the mandatory root dimensions.

tests/agent/mcp/test_drawings.py

@@ -0,0 +1,149 @@
+"""
+MCP text drawing tests: SVG builder units and handler behavior.
+"""
+
+from unittest.mock import MagicMock, patch
+from xml.etree import ElementTree as ET
+
+import pytest
+
+from gns3server.agent.mcp.drawings import build_text_svg, create_text_drawing_handler
+
+BASE = "gns3server.agent.mcp"
+
+
+def _mock_conn(json_result=None):
+    """Create a mocked Gns3Connector with base_url and http_call."""
+    conn = MagicMock()
+    conn.base_url = "http://192.168.1.3:3080/v3"
+    conn.http_call.return_value.json.return_value = json_result or {"status": "ok"}
+    return conn
+
+
+@pytest.fixture
+def ctx():
+    return {"server_url": "http://192.168.1.3:3080", "jwt_token": "token", "jwt_username": "admin"}
+
+
+class TestBuildTextSvg:
+    def test_single_line(self):
+        svg, width, height, line_height = build_text_svg("R1", font_size=13)
+        assert svg == (
+            '<svg height="25" width="21">'
+            '<text fill="#000000" fill-opacity="1.0" font-family="monospace" '
+            'font-size="13" font-weight="normal">R1</text></svg>'
+        )
+        # 2 chars x 13 x 0.8 = 20.8 -> 21; one line of 13 x 1.9 = 24.7 -> 25
+        assert width == 21
+        assert height == 25
+        assert line_height == 25
+
+    def test_bold_and_color(self):
+        svg, _, _, _ = build_text_svg("R1", font_size=13, color="#CC0000", bold=True)
+        assert 'fill="#CC0000"' in svg
+        assert 'font-weight="bold"' in svg
+
+    def test_escapes_xml_characters(self):
+        svg, _, _, _ = build_text_svg("a<b&c", font_size=10)
+        root = ET.fromstring(svg)
+        # round-trips through the parser back to the original text
+        assert root.find("text").text == "a<b&c"
+        assert "a&lt;b&amp;c" in svg
+
+    def test_multi_line(self):
+        svg, width, height, line_height = build_text_svg("hello\nworld!", font_size=10)
+        # longest line is 6 chars x 10 x 0.8 = 48; two lines of ceil(19)
+        assert width == 48
+        assert height == 38
+        assert line_height == 19
+        assert "\n" in ET.fromstring(svg).find("text").text
+
+    def test_proportional_font_wider(self):
+        mono_w, _, _, _ = build_text_svg("same", font_size=10, font_family="monospace")
+        prop_w, _, _, _ = build_text_svg("same", font_size=10, font_family="Noto Sans")
+        assert prop_w > mono_w
+
+    def test_empty_line_kept(self):
+        # a blank line still occupies a line box
+        _, _, height, line_height = build_text_svg("a\n\nb", font_size=10)
+        assert height == 3 * line_height
+
+    def test_matches_web_ui_serializer_shape(self):
+        # byte-for-byte structural parity with the Web UI's own text output
+        svg, width, height, _ = build_text_svg("demo", font_size=11)
+        assert svg.startswith(f'<svg height="{height}" width="{width}"><text fill=')
+        assert svg.endswith("</text></svg>")
+
+
+class TestCreateTextDrawingHandler:
+    def test_success(self, ctx):
+        with patch(f"{BASE}.drawings._get_connector") as m:
+            conn = _mock_conn({"drawing_id": "d1", "x": 100, "y": 80})
+            m.return_value = conn
+            result = create_text_drawing_handler(
+                {"project_id": "p1", "text": "R1", "x": 100, "y": 80, "bold": True}, ctx
+            )
+        assert result["drawing"]["drawing_id"] == "d1"
+        assert result["width"] == 21
+        assert result["height"] == 25
+        # z defaults to 1 (above links)
+        body = conn.http_call.call_args.kwargs["json_data"]
+        assert body["z"] == 1
+        assert body["x"] == 100
+        assert 'font-weight="bold"' in body["svg"]
+
+    def test_missing_project_id(self, ctx):
+        assert "error" in create_text_drawing_handler({"text": "R1"}, ctx)
+
+    def test_missing_text(self, ctx):
+        assert "error" in create_text_drawing_handler({"project_id": "p1"}, ctx)
+
+    def test_blank_text(self, ctx):
+        assert "error" in create_text_drawing_handler({"project_id": "p1", "text": "\n\n"}, ctx)
+
+    def test_newline_normalization(self, ctx):
+        with patch(f"{BASE}.drawings._get_connector") as m:
+            conn = _mock_conn({"drawing_id": "d1"})
+            m.return_value = conn
+            create_text_drawing_handler({"project_id": "p1", "text": "a\r\nb"}, ctx)
+        svg = conn.http_call.call_args.kwargs["json_data"]["svg"]
+        assert "\r" not in svg
+
+    def test_text_too_long(self, ctx):
+        assert "error" in create_text_drawing_handler({"project_id": "p1", "text": "x" * 501}, ctx)
+
+    def test_control_characters_rejected(self, ctx):
+        assert "error" in create_text_drawing_handler({"project_id": "p1", "text": "a\x00b"}, ctx)
+
+    @pytest.mark.parametrize("font_size", [0, 201, "13", 13.5, True])
+    def test_bad_font_size(self, ctx, font_size):
+        result = create_text_drawing_handler({"project_id": "p1", "text": "R1", "font_size": font_size}, ctx)
+        assert "error" in result
+
+    @pytest.mark.parametrize("color", ["red", "123456", "#GGGGGG", "#12345", "black\" onload=\"x"])
+    def test_bad_color(self, ctx, color):
+        result = create_text_drawing_handler({"project_id": "p1", "text": "R1", "color": color}, ctx)
+        assert "error" in result
+
+    @pytest.mark.parametrize("font_family", ['mono" onload="x', "sans<serif>", "a&b", ""])
+    def test_bad_font_family(self, ctx, font_family):
+        result = create_text_drawing_handler({"project_id": "p1", "text": "R1", "font_family": font_family}, ctx)
+        assert "error" in result
+
+    def test_font_family_with_spaces_accepted(self, ctx):
+        with patch(f"{BASE}.drawings._get_connector") as m:
+            conn = _mock_conn({"drawing_id": "d1"})
+            m.return_value = conn
+            result = create_text_drawing_handler(
+                {"project_id": "p1", "text": "R1", "font_family": "DejaVu Sans Mono"}, ctx
+            )
+        assert "error" not in result
+
+    def test_xml_entities_survive_round_trip(self, ctx):
+        with patch(f"{BASE}.drawings._get_connector") as m:
+            conn = _mock_conn({"drawing_id": "d1"})
+            m.return_value = conn
+            create_text_drawing_handler({"project_id": "p1", "text": "R1 & <backup>"}, ctx)
+        svg = conn.http_call.call_args.kwargs["json_data"]["svg"]
+        assert "R1 &amp; &lt;backup&gt;" in svg
+        ET.fromstring(svg)

tests/agent/mcp/test_tool_params.py

@@ -81,6 +81,7 @@ HANDLER_FILES = {
     "restore_snapshot_handler": "snapshots.py",
     "get_drawings_handler": "drawings.py",
     "create_drawing_handler": "drawings.py",
+    "create_text_drawing_handler": "drawings.py",
     "get_drawing_handler": "drawings.py",
     "update_drawing_handler": "drawings.py",
     "delete_drawing_handler": "drawings.py",