Phase 6a: rename core vocabulary (game/main/component/archetype/system)

game/module -> program, main -> entry, component -> property,
archetype -> model, system -> handler. Done via a transitional self-hosting
bootstrap: parser accepts both -> reseed -> compiler source moved to new
keywords + parser tightened to new-only -> reseed (fixpoint holds). Old keywords
now rejected.

Token-safe corpus migration (tools/ludic-tools/rename_kw.c) leaves the LLVM
@main/entry: labels in emit strings untouched; goldens byte-identical. Editor
vocab (header/JetBrains/TextMate/emacs), check-docs wrapper, and doc fences
updated; error string 'unknown component' -> 'unknown property'. test.sh 14/14,
test-tools 28/0, check-vocabulary green. (Doc prose pass to follow.)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

selfhost/main.ludic

@@ -51,7 +51,7 @@ fn die(msg: ptr) -> void {
   os_exit(1)
 }
 
-main {
+entry {
   let path = ptr_null()
   let out  = ptr_null()
   let want = 0            # 0 = auto, 1 = windowed, 2 = headless