[Tutorial] CTable copy() with reblocking and recompression

The CTable.copy() method gained new chunks=, blocks=, and cparams= overrides in this release, but there is no tutorial showing when and why you would use them. There is a standalone example at examples/ctable/copying.py, but no notebook integrated into the tutorial sequence.

Suggested work: Add a notebook 16.ctable-copy.ipynb to doc/getting_started/tutorials/ covering:
- Basic in-memory and persistent copy
- Reblocking: how block size affects SUMMARY index granularity and query pruning
- Recompression: switching codecs (ZSTD → LZ4) and what to expect on size vs speed
- Copying a projected view (select().copy()) to persist a column subset

Start with examples/ctable/copying.py and the existing sequence under doc/getting_started/tutorials/. Add doc/getting_started/tutorials/16.ctable-copy.ipynb covering in-memory and persistent copies, reblocking and SUMMARY query pruning, ZSTD-to-LZ4 recompression tradeoffs, and copying a projected select() view. Done means the notebook is integrated into the tutorial sequence and demonstrates each listed case.

Written by the indexing model from the issue text.