feat: add per-column memory usage

[LuisFigueroaG]

Summary

• adds ArFrame.memory_usage(deep=True) for per-column memory usage
• keeps the existing memory_usage() total-byte behavior unchanged
• documents the new argument and covers the mapping/validation behavior with tests

Closes #2562.

Validation

• uv run ruff format --check arnio/frame.py tests/test_csv.py
• uv run ruff check arnio/frame.py tests/test_csv.py
• uv run pytest -q tests/test_csv.py -k memory_usage
• uv run ruff check .
• uv run pytest -q
• git diff --check

Also attempted:

• uv run ruff format --check . currently reports 34 pre-existing files that would be reformatted
• uv run pyright currently fails because the pyright executable is not present in the uv environment

[vercel]

@LuisFigueroaG is attempting to deploy a commit to the xtylishanish-gmailcom's projects Team on Vercel.

A member of the Team first needs to authorize it.