feat: Adding AGENTS.md repository instructions for AI tooling

AGENTS.md

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+# MQT Core
+
+MQT Core is the backbone of the [Munich Quantum Toolkit (MQT)](https://mqt.readthedocs.io/) — a C++20 and Python library providing core data structures and algorithms for quantum computing design automation. Key components include an intermediate representation (IR) for quantum computations, a state-of-the-art decision diagram (DD) package, a ZX-calculus engine, an OpenQASM 3.0 parser, MLIR-based quantum compilation dialects, and a quantum device management interface (QDMI).
+
+## Tech Stack
+
+| Area                    | Tool                      | Notes                                       |
+| ----------------------- | ------------------------- | ------------------------------------------- |
+| C++ standard            | C++20                     | Minimum required                            |
+| Build system            | CMake 3.24+               | Up to 4.2 supported                         |
+| Python                  | 3.10+                     | Supports 3.10 through 3.14                  |
+| MLIR/LLVM               | 21+                       | Required only when `BUILD_MQT_CORE_MLIR=ON` |
+| Python package manager  | **uv** (>=0.5.20)         | NEVER use pip                               |
+| Python build backend    | scikit-build-core         | With nanobind for bindings                  |
+| Python linter/formatter | **ruff**                  | NEVER use pylint, black, flake8, or isort   |
+| Python type checker     | **ty**                    | NEVER use mypy                              |
+| Python bindings         | **nanobind** (~2.11.0)    | NOT pybind11                                |
+| C++ formatter           | clang-format (LLVM style) |                                             |
+| C++ linter              | clang-tidy                |                                             |
+| CMake formatter         | cmake-format              |                                             |
+| C++ test framework      | Google Test               |                                             |
+| Python test framework   | pytest                    | With pytest-xdist for parallelism           |
+| Pre-commit runner       | prek                      | Wraps pre-commit hooks                      |
+
+## Building the C++ Library
+
+```bash
+# Configure and build (Release)
+cmake -S . -B build -DCMAKE_BUILD_TYPE=Release -DBUILD_MQT_CORE_TESTS=ON
+cmake --build build
+
+# Debug build
+cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug -DBUILD_MQT_CORE_TESTS=ON
+cmake --build build
+```
+
+Key CMake options:
+
+| Option                       | Default                | Description                                                |
+| ---------------------------- | ---------------------- | ---------------------------------------------------------- |
+| `BUILD_MQT_CORE_TESTS`       | ON (if master project) | Build C++ test suite                                       |
+| `BUILD_MQT_CORE_BINDINGS`    | OFF                    | Build Python bindings via nanobind                         |
+| `BUILD_MQT_CORE_MLIR`        | ON                     | Build MLIR quantum compilation dialects (requires LLVM 21) |
+| `BUILD_MQT_CORE_SHARED_LIBS` | OFF                    | Build as shared libraries                                  |
+| `BUILD_MQT_CORE_BENCHMARKS`  | OFF                    | Build evaluation benchmarks                                |
+| `ENABLE_COVERAGE`            | OFF                    | Enable code coverage instrumentation                       |
+
+In-source builds are prevented. External dependencies (nlohmann_json, Boost.Multiprecision, Google Test, spdlog, QDMI, Eigen) are fetched automatically via CMake FetchContent if not found on the system.
+
+## Running C++ Tests
+
+```bash
+# Run the full C++ test suite
+ctest --test-dir build
+
+# Run a single test by name (regex match)
+ctest --test-dir build -R test_dd_package
+
+# Run with verbose output on failure
+ctest --test-dir build --output-on-failure
+
+# Run a specific test binary directly for more control
+./build/test/dd/mqt-core-dd-test
+```
+
+Tests are organized by component under `test/`: `algorithms/`, `circuit_optimizer/`, `dd/`, `ir/` (includes QASM3 parser tests), `na/`, `zx/`, `qdmi/`, `qir/`, `fomac/`. Prefer running targeted tests over the full suite during development.
+
+## Building the Python Package
+
+```bash
+# Install all dev dependencies and build the package in one step
+uv sync
+
+# Build only (produces wheel)
+uv build
+```
+
+Build artifacts are placed in `build/{wheel_tag}/{build_type}/`. The Python package uses scikit-build-core as its build backend with nanobind for C++ bindings.
+
+IMPORTANT: Always use `uv` for dependency management. Never use `pip install`, `pip install -e .`, or any pip-based workflow.
+
+## Running Python Tests
+
+```bash
+# Full test suite (via nox, handles environment setup)
+uvx nox -s tests
+
+# Single test file (if environment is already set up via uv sync)
+uv run pytest test/python/dd/test_dd_package.py
+
+# Single test function
+uv run pytest test/python/dd/test_dd_package.py::test_function_name
+
+# With coverage
+uvx nox -s tests -- --cov
+
+# Test with minimum dependency versions
+uvx nox -s minimums
+
+# Test against latest Qiskit from git
+uvx nox -s qiskit
+```
+
+Python tests live in `test/python/` and use pytest with parallel execution (pytest-xdist). Prefer running individual test files during development.
+
+## Linting and Formatting
+
+```bash
+# Run ALL pre-commit checks (recommended before committing)
+uvx prek run -a
+
+# Alternative via nox
+uvx nox -s lint
+
+# Python type checking only
+uv run ty check
+```
+
+### Pre-commit hook priority order
+
+1. **Validation**: merge conflicts, pyproject schema, GitHub workflows, ReadTheDocs config, capitalization, typos, license headers, uv lockfile sync
+2. **Formatting**: clang-format (C++), cmake-format (CMake), prettier (YAML/MD/JSON), ruff format (Python)
+3. **Linting**: ruff check (Python)
+4. **Type checking**: ty check (Python)
+
+### Ruff configuration
+
+The ruff config in `pyproject.toml` uses `select = ["ALL"]` — **all rules are enabled by default**. Only a small set of rules are selectively disabled. Do not add new rules; only disable specific ones if necessary and document why. Line length is 120. Google-style docstrings are enforced.
+
+### C++ formatting and linting
+
+- clang-format uses LLVM base style with `PointerAlignment: Left` and C++20 standard
+- clang-tidy enforces extensive checks from bugprone, cppcoreguidelines, google, misc, modernize, performance, portability, and readability categories
+
+## Documentation
+
+```bash
+# Build and serve docs locally (requires doxygen installed)
+uvx nox -s docs
+
+# Build without serving (non-interactive)
+uvx nox --non-interactive -s docs
+
+# Check links
+uvx nox -s docs -- -b linkcheck
+```
+
+Documentation uses Sphinx with MyST (Markdown) and the furo theme. Source files are in `docs/`. C++ API docs require doxygen and are integrated via Breathe. MLIR docs are auto-generated from tablegen during the build.
+
+## Type Stubs
+
+```bash
+# Regenerate Python type stubs from nanobind bindings
+uvx nox -s stubs
+```
+
+Stub files (`.pyi`) in `python/mqt/core/` are **auto-generated** by nanobind's stubgen. NEVER edit `.pyi` files manually — they will be overwritten. If bindings change, regenerate stubs and commit the updated `.pyi` files.
+
+## Code Style
+
+### C++
+
+- Formatting: LLVM-based (see `.clang-format`)
+- Naming: `camelBack` for functions, methods, variables, parameters; `CamelCase` for classes, structs, enums; `UPPER_CASE` for global/static constants; `lower_case` for namespaces
+- Indentation: 2 spaces
+- Header guards: `#pragma once`
+
+### Python
+
+- Formatter: ruff format (line length 120)
+- Linter: ruff check with ALL rules enabled
+- Type checker: ty (not mypy)
+- Docstrings: Google style
+- Indentation: 4 spaces
+- Imports: sorted by ruff (isort rules), `from __future__ import annotations` enforced
+
+### CMake
+
+- Keywords: `UPPER_CASE`
+- Line width: 100
+- Formatter: cmake-format (see `.cmake-format.yaml`)
+- Indentation: 2 spaces
+
+### General
+
+- Line endings: LF
+- Charset: UTF-8
+- Trailing whitespace: trimmed (except Markdown)
+- Final newline: required
+
+## Project Layout
+
+```text
+include/mqt-core/     C++ public headers (organized by component)
+src/                   C++ source files (mirrors include/ structure)
+python/mqt/core/       Python package and auto-generated .pyi stubs
+bindings/              nanobind C++ → Python bindings
+test/                  C++ tests (Google Test)
+test/python/           Python tests (pytest)
+cmake/                 CMake modules and helpers
+docs/                  Sphinx documentation source
+mlir/                  MLIR quantum compilation dialects (QC, QCO, QIR)
+eval/                  Benchmarking and evaluation
+json/                  Device configuration files (NA, SC)
+```
+
+Components: `ir` (intermediate representation), `dd` (decision diagrams), `zx` (ZX-calculus), `algorithms`, `circuit_optimizer`, `qasm3` (OpenQASM 3.0 parser), `na` (neutral atoms), `qdmi` (device management), `qir` (QIR runtime), `fomac` (formal methods), `mlir` (MLIR dialects).
+
+## Platform Support
+
+- **Operating systems**: Linux (Ubuntu 24.04), macOS (14, 15), Windows (2022, 2025)
+- **Architectures**: x86_64 and arm64
+- **C++ compilers**: GCC 14+, Clang 20+, MSVC (latest), AppleClang 17+
+- **CI**: GitHub Actions with reusable workflows from `munich-quantum-toolkit/workflows`
+
+## Important Notes
+
+- **License headers are required** on all source files: MIT license, SPDX identifier. Managed by `mz-lictools`. The license-tools pre-commit hook will fail if headers are missing.
+- **Capitalization matters**: use the exact capitalizations "nanobind", "CMake", "ccache", "GitHub", "NumPy", "pytest", "MQT", and "TUM". A pre-commit hook (`disallow-caps`) enforces this and will reject common misspellings.
+- **MLIR caveats**: MLIR is disabled automatically on macOS with GCC (ABI incompatibility) and with AppleClang < 17 (incomplete C++20 support).
+- **Stub files**: Never edit `.pyi` files by hand. Always regenerate with `uvx nox -s stubs`.
+- **uv lockfile**: The `uv.lock` file must stay in sync. The pre-commit hook `uv-lock` checks this. Run `uv lock` if you change dependencies in `pyproject.toml`.
+- **Pre-commit hooks must pass** before submitting pull requests. Run `uvx prek run -a` to check locally.
+- **Test your changes**: all changes must be tested. Write C++ tests with Google Test in `test/`, Python tests with pytest in `test/python/`.