NL2290 does not follow a const alias of an element reference: a stale record is read after a push (native 1, Node 42) #646

Summary

NL2290 refuses a read through a reference to an array element after a push may have moved the array's storage. It does not follow a second const that aliases that reference. The program below compiles. Natively it reads the record from the old storage; under Node it reads the live one.

interface P { x: i32; }
const readX = (p: P): i32 => p.x;
export const main = (): i32 => {
  const ps: P[] = [];
  for (let i: i32 = 0; i < 4; i++) { ps.push({ x: 1 }); }
  const p = ps[0];
  const q = p;                       // alias of the element reference
  for (let i: i32 = 0; i < 1000; i++) { ps.push({ x: 5 }); }
  ps[0].x = 42;
  console.log(`${readX(q)}`);        // NL2290 fires for `p` here, not for `q`
  return 0;
};

• Native, at 1, 2 and 8 threads: prints 1.
• Node: prints 42.

The program is single-threaded. It reproduces on main at 6729c7c and on #644's head.

Notes

• It was found by the round-1 probe of feat(checker): arrow tasks with captures, tasks without a destination, and a seeded Rng #644 (threads-complete task-forms). It is outside that PR: feat(checker): arrow tasks with captures, tasks without a destination, and a seeded Rng #644 adds no code on this path.
• Through a task capture, the same alias (s.spawn(() => readX(q)) after a push) is harmless today. The parent cannot write before the join, and grown storage is not freed. That holds only because of those two facts.
• The fix is to follow const aliases of an element reference in the NL2290 walk, the same way feat(checker): parallelMap, parallelFrom and arrows that read the enclosing function's consts #609's sourceLocal() resolves captures. Each way in needs a negative (CLAUDE.md): const q = p, a chain const r = q, a ternary const q = c ? p : p2, and passing p to a helper that returns it.

Part of #575.