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).
Plan input handling and pattern placement before Game of Life mechanics:
keyboard bindings config, mouse placement with preview/rotation,
HiDPI scaling, and cell grid. Update AGENTS.md project notes.
arek