Support: package simpler and ship runtime assets in wheel

[ChaoWao]

Summary

Direct python tests/.../test_xxx.py runs were failing on from simpler.task_interface import ... because python/ was only on sys.path under pytest. This PR makes simpler (and its dependencies) installable via wheel so any entry point can find it.

Key changes

• python/simpler enters the wheel; the 4 files duplicated with simpler_setup/ (elf_parser, kernel_compiler, runtime_compiler, toolchain) are excluded so the authoritative copies under simpler_setup/ win in wheel mode while source-tree copies remain reachable for un-migrated callers
• src/ (headers + orchestration sources) and build/lib/ (pre-built runtime binaries) are installed under simpler_setup/_assets/ so wheel users get everything kernel compilation needs without a source checkout
• simpler_setup/environment.py::PROJECT_ROOT auto-resolves: _assets/ for wheel install, repo root for source tree / editable
• editable.rebuild = true so the nanobind module auto-rebuilds on import in editable mode (with build-dir = "build/{wheel_tag}" to satisfy the requirement)
• Cleanup: drop ensure_python_path helper + 6 callsites in scene_test.py, drop python/ sys.path insert in run_example.py

Documentation

Updated docs/developer-guide.md, docs/getting-started.md, .claude/rules/architecture.md, .claude/rules/venv-isolation.md to reflect the new packaging model, fix broken import examples (simpler.kernel_compiler → simpler_setup.kernel_compiler), and document the editable-install workflow.

Test plan

• pip install --no-build-isolation -e . succeeds; simpler and simpler_setup both importable
• Wheel build: only stable 4 files of simpler ship; 4 transitional duplicates excluded; _assets/{src,build/lib} populated (296 src + 17 lib files)
• Wheel install in fresh venv: PROJECT_ROOT resolves to _assets/; simpler.task_interface works; simpler.kernel_compiler correctly excluded
• Editable install: PROJECT_ROOT resolves to repo root; editable.rebuild triggers cmake on import
• pytest tests/ut/ — 143 passed, 5 skipped
• Originally-failing direct run python tests/st/.../test_alternating_matmul_add.py no longer hits ImportError (reaches argparse, fails only on missing -p as expected — needs hardware)
• Hardware ST tests (run by reviewer with NPU)

[gemini-code-assist]

Code Review

This pull request restructures the Python package layout by introducing simpler_setup for compilers and build orchestration, while transitioning simpler to a stable user API. It implements dynamic path resolution in simpler_setup/environment.py to support both wheel and editable installs and updates the build system to package assets. Feedback was provided regarding the validity of derived paths in wheel mode and the robustness of using importlib.resources for filesystem path resolution.