fix: Raw code snippet block pruning in unroll

  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;
        // ---
      }"
    `);
  });

Start with the regression test shown in the issue and trace the tgpu.unroll, rawCodeSnippet, and tgpu.resolve entry points. Reproduce the snapshot output, then inspect how raw snippets are handled during unrolled iteration. Done means the snippet remains present once per iteration and the inline snapshot passes.