Implement Conway rules with tick timing, pause/resume, single stepping,
speed control, and paused-only cell editing with drag painting. Update
default key bindings for pause/step/speed. Mark verification complete.
Add configurable key bindings (TOML), modifier-aware dispatch, mouse-driven
pattern placement with preview and rotation, cell grid storage/rendering,
and fractional/integer HiDPI scaling. Archive the input-and-placement change
and sync its specs to main specs.
Tests: Hashtable, Config, Grid, Pattern (4/4 pass).
arek