Replace hardcoded combo count with sizeof expression in test_h3_framing.c

[Copilot]

Addresses review feedback from #590 to replace magic number 6 with a maintainable expression.

Changes

• Move combos array to file scope (static const)
• Replace hardcoded 6 in main_test_pwritev() with sizeof(combos) / sizeof(combos[0])

static const struct { unsigned iovecs, frames; } combos[] =
{
    { 32, 16, },
    { 16, 16, },
    { 16, 8, },
    { 3, 7, },
    { 7, 3, },
    { 100, 100, },
};

static void main_test_pwritev(void) {
    main_test_pwritev_combo(0, sizeof(combos) / sizeof(combos[0]));
}

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[dtikhonov]

This is too complicated, @copilot. Just replace "6" with "sizeof(combos) / sizeof(combos[0])" and be done with it.

[Copilot]

This is too complicated, @copilot. Just replace "6" with "sizeof(combos) / sizeof(combos[0])" and be done with it.

Simplified in c86ca9b - moved combos to file scope and replaced 6 with sizeof(combos) / sizeof(combos[0]).