* fix(#2279): reword date stamping to overwrite existing dates on Update runs
The map-codebase agent and workflow instructions only said to replace
[YYYY-MM-DD] placeholders, but Update-path files already contain concrete
dates from the prior run. Reword to SET the date stamps unconditionally,
overwriting whatever date is already there.
Closes#2279
* docs(#2279): backfill changeset PR number (2550)