feat: #get property accessors (no-paren method-as-field)

A method declared `name :: (self: *T) -> R #get => expr;` is invoked via
no-paren field syntax (`obj.name`) instead of `obj.name()`. It is an ordinary
method (registered `Type.method`, flagged is_get); field-access lowering and
inference dispatch to it when no real field of that name exists, by synthesizing
a no-arg `obj.name()` call routed through the normal call path (so receiver
address-of and generic binding are reused).

- Lexer/token: `#get`. Parser: parsed after the return type in parseFnDecl;
  hasFnBodyAfterArrow treats it as a body marker so struct-body methods parse.
- Resolution: getAccessorFor handles a generic-struct instance and a plain
  struct. A REAL field of the same name wins (a getter never shadows stored
  data). An explicit postfix-deref receiver (`p.*.getter`) dispatches on the
  inner pointer so it takes the working auto-deref path.
- Works on plain + generic structs (incl. getters returning the type param),
  in expressions/conditions/args/loop-bounds, chained, and via a pointer
  receiver. Examples: types/0196 (basic) + types/0197 (stress).

Known narrow limitations (clean errors / workarounds, not silent): a getter
RESULT used directly as a method/getter receiver (`o.gi.dbl`) errors — bind it
to a local first; a getter named `len`/`ptr` returning non-i64 mis-infers
(the .len/.ptr builtin-field shortcut).

src/ast.zig

@@ -192,6 +192,10 @@ pub const FnDecl = struct {
     /// OPT-IN: only `is_ufcs` fns and `ufcs` aliases dispatch; a plain
     /// fn is callable directly or via `|>` only.
     is_ufcs: bool = false,
+    /// `name :: (self: *T) -> R #get => expr;` — a no-paren property accessor.
+    /// Invoked via field syntax (`obj.name`) when no real field matches, rather
+    /// than as a `obj.name()` call. Takes only the `self` receiver.
+    is_get: bool = false,
 };
 
 pub const Param = struct {