[codex] Update PTODSL public API docs and surface

[zhoubot]

Summary

• update the top-level PTODSL docs to match the current public API and A5/micro flow
• restore the latest public package surface with pythonic pto helpers, a package-level micro module, and missing dtype aliases
• add regression coverage for the public API wrapper path and raw micro imports

Why

The repo had recent PTODSL and A5 upgrades, but the top-level documentation and package exports had drifted behind the code. The package root did not expose micro, the public pto surface was missing the newer pythonic tensor/tile builders, and some dtype aliases used by the newer A5 code were not available through the shared surface.

Impact

• users can import the documented ptodsl.pto and ptodsl.micro surfaces directly
• the README and API notes now describe the current PTODSL -> PTOAS -> HIVM flow
• wrapper objects produced by the pythonic pto facade interoperate with the existing low-level tile ops

Validation

• PYTHONPATH=/Users/zhoubot/github/.llvm-19.1.7/build-mlir-py312/tools/mlir/python_packages/mlir_core:/Users/zhoubot/github/pto-org/PTOAS/install-src312:/Users/zhoubot/github/pto-org/PTOAS/build-src312/python /Users/zhoubot/github/.venv-ptoas-src312/bin/python -m pytest -q tests/frontend tests/regression
• result: 70 passed in 1.04s