Add an 'update data' how-to

[dimitri-yatsenko]

The book's updates chapter (40-operations/030-updates.ipynb) frames updates as rare and deliberate — prefer delete + reinsert + recompute; update1() is a surgical correction, not a normal workflow operation. The docs have no how-to counterpart; update1() / when-to-update guidance is scattered across explanation pages and specs.

Proposal: add how-to/update-data.md (or a section in an existing how-to) covering when updates are appropriate, update1() usage, and the delete-reinsert-recompute pattern for correcting computed results.

From an internal datajoint-book → docs coverage review (priority P7).

[dimitri-yatsenko]

Addressed by #226, which added the how-to/update-data.md how-to — updates are rare and surgical, prefer delete + reinsert (+ recompute), update1() for single-row corrections. Closing.