Remove the (tex_x || tex_y) guard in tilemap_render_layer() that
silently ignored TileDefs pointing to tileset position (0,0). The
tile_def_count check alone is sufficient to distinguish defined from
undefined tiles.
Sync the editor palette to use TileDef tex coords when available,
fixing the mismatch where the palette showed tiles by sequential grid
position while the canvas used TileDef coordinates.
Save all TileDef entries unconditionally to prevent round-trip data
loss for tiles at position (0,0) with no flags.
Track the active level file path so pressing E during gameplay opens
the editor with that level loaded instead of a blank canvas.
Introduce moon01.lvl as the starting level — a pure jump-and-run intro
with no gun and no enemies, just platforming over gaps and dodging falling
asteroids. The player picks up their gun upon transitioning to level01.
New features:
- Moon tileset and PARALLAX_STYLE_MOON with crater terrain backgrounds
- Asteroid entity (ENT_ASTEROID): falls from sky, damages on contact,
explodes on ground with particles, respawns after delay
- PLAYER_UNARMED directive disables gun for the level
- Pit rescue mechanic: falling costs 1 HP and auto-dashes upward
- Gun powerup entity type for future armed-pickup levels
- Segment-based procedural level generator with themed rooms
- Extended editor with entity palette and improved tile cycling
- Web shell improvements for Emscripten builds
