rename render/ files to UpperCamelCase to match client convention

The render/ tree was the only place in the client still using kebab-case
filenames. Brings ~80 files in line with the rest of src/client/
(BuildPreviewController, TransformHandler, etc.). Directories kept as
they were (name-pass/, fx-pass/, passes/, utils/, debug/) since the
codebase already mixes those.

Two collisions surfaced and got resolved: render/types/ is a directory,
not a file, so its imports kept the lowercase form; and the sed pass
incidentally normalized core/pathfinding imports, which had to be
reverted since that file is actually lowercase on disk despite some
imports having referenced it as ./Types under macOS case-insensitive
resolution.

src/client/WebGLFrameBuilder.ts

@@ -1,6 +1,6 @@
 import { Colord } from "colord";
 import { GameView } from "../core/game/GameView";
-import { uploadFrameData } from "./render/frame/upload";
+import { uploadFrameData } from "./render/frame/Upload";
 import { PlayerStatic, GameView as WebGLGameView } from "./render/gl";
 
 const PALETTE_SIZE = 4096;