New features

Reworked the select tool: selections can now be resized by dragging edge/corner handles, and bucket fill now respects the active selection for full or hollow (border) regions.
Added a tile grid overlay and a pixel grid for the selected tile, each with a configurable minimum zoom before auto-hiding and an optional axis-color highlight.
Added keybinds for toggling the tile grid (G) and pixel grid (Shift+G).
Added a "Focus windows on hover" option to focus editor windows when hovered.

Fixes

Fixed a regression that dropped underlay outline (sprite edge) rendering.
Fixed #if 0 (and other inactive preprocessor branches) leaking lexer errors from code inside the dead branch.
Fixed DM string literals not decoding escape sequences (\n, \t, \r, \, ", ', [, ]).
Fixed unbounded memory growth from interned symbols never being freed.
Hardened the parser and object tree against panics: the parser now rejects a file once its expression limit is hit instead of overflowing, and a parent_type cycle is now rejected instead of corrupting the tree.