Drop the duplicate Manager, use inkwell's

The engine already had the registry the game was reimplementing:
inkwell.Manager[T Named], and every entity type here is an alias of an
engine struct, so they all carry GetName() already. manager.manager.go
and manager.interface.go are gone; a category manager is now one call to
inkwell.NewManager.

registerAll goes with it — Each does the hand-off — and the selector
writes its derived pins back with Set, which keeps the scene in place in
the registration order.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

go.sum

@@ -1,7 +1,5 @@
-git.teletypegames.org/engines/inkwell v0.1.0 h1:NJgT924aR3e0uLVRiTEhzLrXJY+Vnj+FArkKqMJJlVI=
-git.teletypegames.org/engines/inkwell v0.1.0/go.mod h1:/v6QtismTE8+e7kobbVR5B/CpTSrd4j2DYwJ8DvINhs=
-git.teletypegames.org/engines/inkwell v0.1.1-0.20260829220920-f9745e426624 h1:lzKbik6RzcqIEub13X8a1J3V/MCQOPNo2XF8oOKm+Ts=
-git.teletypegames.org/engines/inkwell v0.1.1-0.20260829220920-f9745e426624/go.mod h1:/v6QtismTE8+e7kobbVR5B/CpTSrd4j2DYwJ8DvINhs=
+git.teletypegames.org/engines/inkwell v0.1.1-0.20260830075028-08f15a7e3d11 h1:DPN74Xy0xcyelfh5xLuv6XBj6wrdzKVME1a1HyACsj4=
+git.teletypegames.org/engines/inkwell v0.1.1-0.20260830075028-08f15a7e3d11/go.mod h1:/v6QtismTE8+e7kobbVR5B/CpTSrd4j2DYwJ8DvINhs=
 github.com/ebitengine/gomobile v0.0.0-20250923094054-ea854a63cce1 h1:+kz5iTT3L7uU+VhlMfTb8hHcxLO3TlaELlX8wa4XjA0=
 github.com/ebitengine/gomobile v0.0.0-20250923094054-ea854a63cce1/go.mod h1:lKJoeixeJwnFmYsBny4vvCJGVFc3aYDalhuDsfZzWHI=
 github.com/ebitengine/hideconsole v1.0.0 h1:5J4U0kXF+pv/DhiXt5/lTz0eO5ogJ1iXb8Yj1yReDqE=