ADR-0017 added --force-conversion / --dont-convert as
opt-in flags on `change column`; the help text already
mentioned the flags but didn't explain when they apply.
ADR-0018 generalised serial beyond PK and added auto-fill
on `add column ... (serial|shortid)` for non-empty tables;
none of that was reflected in user-visible help.
This commit:
- Annotates the `add column` line with a continuation note
that adding serial/shortid to a non-empty table
auto-fills existing rows.
- Annotates the `change column` line with a continuation
note that converting to serial/shortid auto-fills null
cells.
- Appends an "Auto-generated types" section explaining
serial and shortid: how they auto-fill, that they imply
UNIQUE outside a PK (serial) or always (shortid), and
that adding/converting-to either type on a non-empty
table auto-fills existing/null cells.
The new test
`help_describes_auto_generated_type_behaviour` pins these
phrases so a future help-text edit can't silently drop the
pedagogical lines. The existing
`help_command_lists_supported_commands` and
`help_lists_export_and_import` tests still pass — they
only assert substring presence.
No engine vocabulary leaks (ADR-0002 posture preserved).
536 -> 537 passing, clippy clean.
claude@clouddev1
3dbaedc1da