fix: Raw code snippet block pruning in unroll

[aleksanderkatan]

  it('does not break with raw code snippets', () => {
    const snip = tgpu['~unstable'].rawCodeSnippet('const a = 1', d.Void);

    const fn = () => {
      'use gpu';
      for (const a of tgpu.unroll([1, 2, 3])) {
        snip.$;
      }
    };

    expect(tgpu.resolve([fn])).toMatchInlineSnapshot(`
      "fn fn_1() {
        // unrolled iteration #0
        const a = 1;
        // unrolled iteration #1
        const a = 1;
        // unrolled iteration #2
        const a = 1;
        // ---
      }"
    `);
  });

[pullfrog]

  ^{｜ Build this ➔ ｜ Make a plan ➔}

[huytdps13400]

Regression PR is open: #2921.

The maintainer-provided case already resolves correctly on current main, so I kept this test-only: it pins all three raw snippet emissions inside the unrolled WGSL and avoids an unnecessary resolver change. Source and built attest suites, types, style, and circular-dependency checks pass.

[aleksanderkatan]

It was not requested. This is an error. The aim of this issue is to fix this snapshot, which is obviously invalid.