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>

docs/language/system/system-file_open.md

@@ -4,7 +4,7 @@ name: System.file_open
 category: system
 kind: namespace-method
 tokens: System.file_open
-sig: System.file_open(path, mode) -> ptr
+sig: System.file_open(path, mode) -> pointer
 tip: Open a file.
 order: 6
 ns: System

docs/language/system/system-stderr.md

@@ -4,7 +4,7 @@ name: System.stderr
 category: system
 kind: namespace-method
 tokens: System.stderr
-sig: System.stderr() -> ptr
+sig: System.stderr() -> pointer
 tip: The standard error handle.
 order: 13
 ns: System

docs/language/system/system-stdout.md

@@ -4,7 +4,7 @@ name: System.stdout
 category: system
 kind: namespace-method
 tokens: System.stdout
-sig: System.stdout() -> ptr
+sig: System.stdout() -> pointer
 tip: The standard output handle.
 order: 12
 ns: System