feat: Granular tracking of stale references

There has been TypeScript behavior that we have overlooked up until now that has to do with references:

const Boid = d.struct({
  pos: d.vec3f,
  vel: d.vec3f,
});

function main() {
  'use gpu';
  const boid = Boid();
  // getting a reference to the boid's position
  const boidPos = boid.pos;
  // replacing the `pos` property of the boid with a new vector
  boid.pos = d.vec3f(1, 2, 3);
  // returning the `x` coordinate of the vector that was once
  // the boid's position
  return boidPos.x;
}

We'd expect the result of main() to be 0, since we haven't actually updated the x coordinate of the existing boid.pos, rather we replaced that vector with an entirely new one, making boidPos no longer point to the actual value of boid.pos (they drifted out of sync).
We generate the following WGSL:

struct Boid {
  pos: vec3f,
  vel: vec3f,
}

fn main() -> f32 {
  var boid = Boid();
  let boidPos = (&boid.pos);
  boid.pos = vec3f(1, 2, 3);
  return (*boidPos).x;
}

In the generated WGSL, boidPos is a pointer to boid.pos, meaning it always reflects the up-to-date value of boid.pos, making the result of calling main() be 1.

Stale reference tracking

@cieplypolar's insight is that we can use a sort of borrow checker (like we were planning to do for consumption verification) to invalidate stale references. Essentially, as soon as it's determined that boid (the original value) could have been mutated by an instruction, boidPos would become invalidated and unaccessible.

struct Boid {
  pos: vec3f,
  vel: vec3f,
}

fn main() -> f32 {
  var boid = Boid();
  let boidPos = (&boid.pos);
  boid.pos = vec3f(1, 2, 3); // <- accessing the original invalidates the aliases
  return (*boidPos).x; // 🚫 `boidPos` is a stale reference
}

I believe there is a way to do this statically without introducing too much complexity to the system.

[!NOTE]
To be continued...

function main() {
  'use gpu';
  const boid = Boid();
  // boid
  //

  const boidPos = boid.pos;
  // boid
  // |
  // | (.pos)
  // |
  // boidPos

  randomFunction(boid) // <- arguments are immutable, so this is okay

  blackBox(d.ref(boid)); // <- could mutate `boid`
  // boid
  // |
  // | (.pos)
  // |
  // ☠️ boidPos

  return boidPos.x; // 🚫 `boidPos` is a stale reference
}

function main() {
  'use gpu';
  const boid = Boid();
  // boid
  //

  const boidPos = boid.pos;
  // boid
  // |
  // | (.pos)
  // |
  // boidPos

  const boidVel = boid.vel;
  // boid
  // |         \
  // | (.pos)   \ (.vel)
  // |           \
  // boidPos      boidVel

  blackBox(d.ref(boid)); // <- could mutate `boid`
  // boid
  // |         \
  // | (.pos)   \ (.vel)
  // |           \
  // ☠️ boidPos   ☠️ boidVel

  return boidPos.x; // 🚫 `boidPos` is a stale reference
}

No files or tests are identified in the issue. Start by tracing the TypeScript-to-WGSL reference generation and the existing consumption-verification work mentioned in the proposal. Done means references become inaccessible after the original value may be mutated, while immutable argument use remains valid.