refactor(lang): rename the ptr/ptrs types to pointer/pointers

Expand the abbreviated pointer types to full words on the language surface:
  ptr   ->  pointer     (a raw address / FFI handle)
  ptrs  ->  pointers    (a buffer of pointers)

The Ludic type name is distinct from LLVM's own `ptr` spelling: llty() maps
`pointer`/`pointers` to LLVM `ptr`, and the emitted IR keeps `ptr`, so only
the Ludic-level surface changes. Rewrites type annotations across all
sources, the 8 hardcoded pointer type-tags, the `pointers`-buffer indexing
in emit_addr, the grammars/LSP/JetBrains tokens, and the docs
(type-ptr -> type-pointer, type-ptrs -> type-pointers). int/bool keep their
conventional short spelling (like Math).

Reseeded; C-free fixpoint holds; all suites green (45/24/29); site + check.py OK.

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

tools/x/main.ludic

@@ -43,7 +43,7 @@ program X {
   }
 
   # a positional argument, or a default when absent
-  function argn(i: int, dflt: ptr) -> ptr {
+  function argn(i: int, dflt: pointer) -> pointer {
     if (i < arg_count()) { return arg(i) }
     return dflt
   }