claude@clouddev1
eff2ee8d14
Expand ColumnSpec and Command::AddColumn with the four ADR-0029 constraint slots (not_null, unique, default, check), all defaulting off; `Database::add_column` now takes a ColumnSpec. No behaviour change — the grammar to set the fields and the DDL to enforce them land in the following commits. Isolated here so those commits stay readable. Adds ColumnSpec::new for the unconstrained case; 110 call sites updated. 1172 tests pass; clippy clean.