feat(map-editor): v0.2.0c — transform controls + Direct-mode override paint

State + actions:
 - active_flip (0/1) joins active_rot (0..3). Combined the two cover
   all 8 D4 orientations; single Flip button is sufficient (H+V
   would be redundant).
 - toggle_flip / reset_transform / paint_override_at /
   erase_override_at.

Toolbar:
 - New Flip (H) + Reset (0) buttons next to Rotate (R).
 - Status chip extended with `slot=N rot=N flip=N` indicator.

Paint:
 - Direct-mode + LMB on canvas now calls maps.set_override on the
   active material-bound terrain layer. Bare slot int when canonical
   (rot=0+flip=0), {slot, rot, flip} object otherwise — matches the
   v0.5.1 override-format extension. Palette slot 1..14 maps to lib
   slot 0..13 (palette is user-friendly 1-based; lib API is 0-based).
 - Direct-mode + RMB on canvas calls maps.clear_override.
 - Auto-Tile mode unchanged; transform state is ignored there (the
   renderer derives slot/rot/flip from the vertex bitmask).

Hotkeys:
 - h -> flip (new)
 - 0 -> reset_transform (new)
 - r continues to cycle rotation CW; Shift+R for CCW is out because
   lib-core.input has no modifier-combo support (deferred).

Cheatsheet rows updated.

manifest.module

@@ -1,6 +1,6 @@
 {
     "id": "map-editor",
-    "version": "0.2.0b.1",
+    "version": "0.2.0c",
     "kind": "module",
     "api": "^0.1",
     "ci_frames": 30,