feat(lang): new Type { field: value } record initialisers

`new` accepted only a bare `new T` (every field its declared default) or
`new []T`, but the docs (kw-new) document `new Record { field: value, … }`
as the way to construct a record with non-default fields — a documented,
intended form the parser never accepted (`let o = new Point { x: 3 }` failed
with "expected newline or ';'").

Parse an optional `{ … }` override record after the type in a `new`
expression (reusing the existing `record()` parser that `spawn` uses), and
seed each field in emit_new_struct from that record when present, else from
the field's declared default. `new []T` and bare `new T` are unchanged.

Also mark the illustrative kw-import fence `# doc-check: skip` (its imports
are example paths that can't resolve in isolation), which makes `x check-docs`
fully green (398 fences, 0 drifted) — so it is now wired as a gate in
`x test-tools` and CI, guarding against future doc/compiler drift.

Reseed is a clean fixpoint (x bootstrap-cfree holds); x test (56),
x selfhost-test (29, golden renders unchanged) and x test-tools (30) green.

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

selfhost/frontend/parse.ludic

@@ -149,7 +149,7 @@ function p_primary() -> Node {
     if (t.text == "true")  { let n = node(E_BOOL); n.ival = 1; pi = pi + 1; return n }
     if (t.text == "false") { let n = node(E_BOOL); n.ival = 0; pi = pi + 1; return n }
     if (t.text == "null")  { pi = pi + 1; return node(E_NULL) }
-    if (t.text == "new")   { pi = pi + 1;  let n = node(E_NEW); n.s = ptype(); return n }
+    if (t.text == "new")   { pi = pi + 1;  let n = node(E_NEW); n.s = ptype();  if is_op("{") { n.a = record() };  return n }
     let n = node(E_ID); n.s = t.text; pi = pi + 1; return n
   }
   if is_op("(") { pi = pi + 1; skipnl(); let e = expr(); skipnl(); eat_op(")"); return e }