feat: initial numpcpp import — C++ numpy pixel-level alignment

Import core.h/cpp, linalg.h/cpp, einsum.h/cpp, and test_einsum.py
from melange tpp_onemodel_cpp/numpy/.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: peng.li24

CMakeLists.txt

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+cmake_minimum_required(VERSION 3.16)
+project(numpycpp VERSION 0.1.0 LANGUAGES CXX)
+
+# C++20
+set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
+
+if(NOT CMAKE_BUILD_TYPE)
+    set(CMAKE_BUILD_TYPE Release)
+endif()
+
+# Dependencies
+find_package(Python3 COMPONENTS Interpreter Development REQUIRED)
+find_package(pybind11 CONFIG REQUIRED)
+find_package(Eigen3 3.3 REQUIRED NO_MODULE)
+
+# Collect sources
+file(GLOB SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/numpy/*.cpp)
+
+# Headers
+include_directories(${CMAKE_CURRENT_SOURCE_DIR})
+
+# Python module
+pybind11_add_module(numpycpp ${SOURCES})
+
+target_include_directories(numpycpp PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
+target_link_libraries(numpycpp PRIVATE Eigen3::Eigen)
+
+set_target_properties(numpycpp PROPERTIES
+    PREFIX ""
+    SUFFIX ".so"
+    LIBRARY_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
+)
+
+# Install
+install(TARGETS numpcpp
+    LIBRARY DESTINATION ${Python3_SITEARCH}
+)
+
+install(DIRECTORY numpy/
+    DESTINATION include/numpycpp
+    FILES_MATCHING PATTERN "*.h"
+)
+
+message(STATUS "numpycpp v${PROJECT_VERSION}")
+message(STATUS "  C++ Standard: ${CMAKE_CXX_STANDARD}")
+message(STATUS "  Python:       ${Python3_VERSION}")
+message(STATUS "  Eigen3:       ${EIGEN3_INCLUDE_DIR}")

README.md

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+# numpcpp
+
+C++ pixel-level alignment of Python numpy, powered by Eigen.
+
+## Overview
+
+`numpycpp` provides a C++ implementation of numpy's core API (`numpy.*`, `numpy.linalg.*`, `numpy.einsum`), designed for seamless pybind11 integration. Every function mirrors Python numpy's signature and semantics.
+
+## Dependencies
+
+- C++20
+- [pybind11](https://github.com/pybind/pybind11)
+- [Eigen3](https://eigen.tuxfamily.org/) >= 3.3
+
+## Build
+
+```bash
+mkdir build && cd build
+cmake .. -DCMAKE_BUILD_TYPE=Release
+make -j$(nproc)
+```
+
+## Usage
+
+```python
+import numpcpp
+```
+
+## License
+
+MIT