fix: Allow break inside a switch inside an unrolled loop

[dchaudhari7177]

Fixes #3068.

Cause

WgslGenerator rejects every break while #unrollingChain is non-empty ("Cannot unroll loop containing break"). A break inside a switch exits the switch, not the loop, and the switch is still there after unrolling. So this threw:

for (const foo of tgpu.unroll([1, 2])) {
  switch (mode) {
    case 0:
      r += foo;
      break;
    default:
      r -= foo;
      break;
  }
}

Fix

A new #breakExitsSwitch flag says whether the innermost statement a break would exit is a switch.

• While a switch's case consequents are generated, it is true.
• For each unrolled iteration's body it is reset to false. An unrolled loop nested inside a switch case therefore still rejects a break of its own, which would otherwise end up exiting the switch after unrolling.
• break is rejected only when unrolling and the flag is false.
• continue is unchanged: inside a switch it still targets the unrolled loop, so it still throws.

Ordinary for/while loops already reset #unrollingChain, so break inside them was never affected.

Tests (tests/unroll.test.ts)

• break in a runtime switch inside tgpu.unroll: unrolls, one switch per iteration, and the trailing breaks are pruned as usual.
• The same with a comptime-known discriminant (the folded single-default switch).
• continue in a switch inside the unrolled loop still throws "Cannot unroll loop containing continue".
• An unrolled loop with a break nested inside a switch case still throws "Cannot unroll loop containing break".

On main the first two fail. On this branch, packages/typegpu gives 192 files, 2735 passed, and packages/typegpu-gl passes. oxfmt is clean.

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[pullfrog]

✅ No new issues found.

Reviewed changes

• break in a switch inside an unrolled loop — added a #breakExitsSwitch flag to WgslGenerator that is set while generating a switch case consequent and reset per unrolled iteration, so break is only rejected when it would actually exit the unrolled loop.
• Tests — four new cases in unroll.test.ts covering the runtime-discriminant switch, the comptime-folded switch, continue still throwing, and a break in an unrolled loop nested inside a switch case still throwing.

I traced the flag through nested switches, switches in unrolled loops, unrolled loops in switch cases, and runtime for/while loops nested in either (these reset #unrollingChain, so they need no flag handling). Save/restore via finally is correct in every path. I also confirmed the two positive tests fail with the fix condition reverted to the base form, so they genuinely pin the change. The full packages/typegpu suite (2735 tests) and packages/typegpu-gl (118 tests) pass; GlslGenerator inherits _statement, so it picks up the fix.

  ^{｜ View workflow run ｜ Using deepseek-v4.1-flash (free via Pullfrog for OSS) ｜ 𝕏}