supports transform & scale (#10)

* src/naive_svg.hpp：
  - SVG 类新增 transform_ 成员变量和 fluent API (svg.transform("scale(1,-1)"))
  - write() 方法：当 transform_ 非空时，用 <g transform='...'>...</g> 包裹所有内容（grid + elements），缩进也相应调整

  src/pybind11_naive_svg.cpp：
  - 新增 SVG.transform() 的 Python 绑定

  用法示例：

  svg = SVG(800, 600)
  svg.view_box([xmin, ymin, width, height])

  # ENU: Y 轴翻转
  svg.transform("scale(1,-1) translate(0,-{})".format(ymin + ymax))

  # Ego (x→front, y→left): 旋转 + 翻转
  svg.transform("rotate(-90) scale(1,-1)")

  所有尺寸（stroke-width, r, font-size）都在世界坐标单位下，用户自己按米估量。

* fix headers

* update stub

* init CLAUDE.md

* add skill.md

* fix

---------

Co-authored-by: tang zhixiong <zhixiong.tang@momenta.ai>

Author: district10

CLAUDE.md

@@ -0,0 +1,54 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+**naive-svg** is a C++/Python hybrid library for SVG generation with GeoJSON-to-SVG conversion. C++ core (`src/naive_svg.hpp`) provides SVG primitives via a fluent API, exposed to Python through pybind11 bindings (`src/pybind11_naive_svg.cpp`). A pure-Python module (`src/naive_svg/geojson2svg.py`) handles GeoJSON conversion with WGS84/ENU coordinate transforms.
+
+## Build & Development Commands
+
+```bash
+# Build (editable install with C++ compilation)
+make build
+
+# Run tests
+make pytest                    # runs pytest tests/test_basic.py
+pytest tests/test_basic.py     # core tests
+pytest tests/test_geojson_showcase.py -v -s  # showcase with SVG output
+
+# Lint (runs pre-commit hooks: ruff, clang-format, cmake-format, mypy)
+make lint
+
+# Regenerate type stubs after changing C++ bindings
+make restub    # runs pybind11-stubgen, copies to src/naive_svg/_core.pyi
+```
+
+## Architecture
+
+### Two-layer design
+
+1. **C++ layer** (`src/naive_svg.hpp`): All SVG types live in `namespace cubao` under `struct SVG`. Element types: `Color`, `Polyline`, `Polygon`, `Circle`, `Text`, `Path`, `Rect`. The `SVG` class is the container that holds elements and produces SVG XML via `write()`/`to_string()`/`dump()`.
+
+2. **Python layer** (`src/naive_svg/`): `_core` is the compiled pybind11 module. `geojson2svg.py` adds GeoJSON parsing, coordinate conversion (via `pybind11_geobuf`), and layered styling.
+
+### Fluent API pattern
+
+The C++ macro `SETUP_FLUENT_API(Klass, VarType, VarName)` generates getter/setter pairs where setters return `Klass&` for chaining. A corresponding pybind11 macro `SETUP_FLUENT_API_PYBIND` mirrors this in Python bindings. When adding new element properties, update both macros.
+
+### Key conventions
+
+- All Python files require `from __future__ import annotations` (enforced by ruff isort).
+- C++ formatted with `.clang-format`; Python with `ruff format`.
+- Type stubs in `stubs/naive_svg/_core.pyi` are auto-generated — edit the C++ bindings, then `make restub`.
+- The C++ header is canonical and synced upstream to `cubao-headers` via `make sync_headers`.
+
+## Source Layout
+
+- `src/naive_svg.hpp` — C++ SVG library (single header)
+- `src/pybind11_naive_svg.cpp` — pybind11 bindings
+- `src/main.cpp` — PYBIND11_MODULE entry point
+- `src/naive_svg/geojson2svg.py` — GeoJSON-to-SVG converter (pure Python)
+- `src/naive_svg/_core.pyi` — auto-generated type stubs
+- `tests/test_basic.py` — unit tests for C++ bindings and geojson2svg
+- `tests/test_geojson_showcase.py` — integration test generating showcase SVG

Makefile

@@ -46,7 +46,7 @@ test_in_dev_container:
 
 PYTHON ?= python3
 build:
-	$(PYTHON) -m pip install scikit_build_core pyproject_metadata pathspec pybind11
+	$(PYTHON) -m pip install scikit_build_core pyproject_metadata pathspec pybind11 cubao_headers
 	CMAKE_BUILD_PARALLEL_LEVEL=$(NUM_JOBS) $(PYTHON) -m pip install --no-build-isolation -Ceditable.rebuild=true -Cbuild-dir=build -ve.
 python_install:
 	$(PYTHON) -m pip install . --verbose
@@ -63,7 +63,7 @@ pytest:
 restub:
 	pybind11-stubgen naive_svg._core -o stubs
 	cp stubs/naive_svg/_core.pyi src/naive_svg
-	pre-commit run --files src/naive_svg/_core.pyi
+	pre-commit run --files src/naive_svg/_core.pyi >/dev/null 2>&1 || true
 
 # conda create -y -n py38 python=3.8
 # conda create -y -n py39 python=3.9