feat(types): option (some/none) safety type (#53)

Types phase 3 — the option/result safety pair. result/ok/err/try shipped in
#46; this adds its companion option:

- some(v)   -> option   (present value; any i32-width scalar)
- none()    -> option   (empty; no magic -1 sentinel)
- is_some / is_none -> bool
- unwrap_or(o, fallback) -> int

A heap %Option = { i32 present, i32 value }, bare builtins guarded by find_fn
(a user fn of the same name still wins), gated by g_uses_option so unused
programs compile byte-identically — same idiom as result.

Wired: emit_call codegen + %Option decl (emit_decl) + g_uses_option (emit_core),
reseeded seed, vocabulary sync (header/JetBrains/TextMate), builtin docs +
inventory, and a self-asserting example (examples/library/optionresult.ludic +
feat_case). All suites green incl. golden renders byte-identical and the
bootstrap fixpoint.

Tagged-union enums (variant payloads + binding match + exhaustiveness) are the
deep type-system feature, split out to #56.

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

changes/types-option.md

@@ -0,0 +1,11 @@
+bump: minor
+type: feat
+**`option` — a maybe-a-value type (#53, types phase 3).** The companion to
+`result` (#46): `some(v)` wraps a present value (any i32-width scalar), `none()`
+is the empty case — a missing value with no magic `-1` sentinel — and
+`is_some`/`is_none`/`unwrap_or(o, fallback)` test and read it. A heap
+`%Option = { i32 present, i32 value }`, additive and gated, so a program that
+does not use it compiles byte-identically. With `result`/`ok`/`err`/`try`
+already shipped, the concrete option/result safety types of phase 3 are done;
+general tagged-union enums (variant payloads + binding `match` + exhaustiveness)
+are tracked separately in #56.