[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