fix: guard y-axis tick loop against float stall

[NemeZZiZZ]

Problem

The y-axis tick loop has no stall guard:

while (f <= last) {
  ...
  f += interval   // if interval < ULP(f)/2, f never changes → infinite loop
}

In IEEE-754, when interval is smaller than half the ULP of f, the addition leaves f unchanged and the loop never terminates — ticks grows without bound (frozen tab, eventually OOM).

Verified by execution: with a flat range at magnitude ~1e13 (ulp(1e13) ≈ 1.95e-3) — reachable because createRangeImp expands a degenerate range to TICK_COUNT * minSpan where minSpan = 1e-4 at precision 4 — interval = nice(8e-4 / 8) = 1e-4, and 1e13 + 1e-4 === 1e13. The loop did not terminate within 1,000,000 iterations, with f pinned at 10000000000000.

Fix

Break when the addition stops moving the accumulator:

const next = f + interval
if (next === f) { break }
f = next

Verification

• Stall scenario: terminates after the first tick instead of hanging.
• Normal cases byte-identical: [100,108] step 1 → 100..108 (9 ticks); [0.05,0.4] step 0.05 → 0.05..0.4 (8 ticks).