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Fix 100% CPU usage from resizeEvent feedback loop under fractional scaling
KCalculator::resizeEvent() forces the window to minimumSize() whenever the current size is smaller, by calling resize(). That resize() delivers another resizeEvent, which re-runs the same check.
size() and minimumSize() are integer QSizes. Under fractional display scaling (I'm running at 150% on X11: KCalc 22.12.3, Qt 5.15.8, KF5 5.103.0, Plasma/KWin 5.27.5, kernel 6.12.43+deb12-amd64, Debian 12 "bookworm") Qt rounds scaled geometry to whole device pixels, and the rounded minimumSize() and the rounded realized window size can differ by one pixel. The exact "<" comparison therefore stays true on every pass, so the window resizes itself in a tight loop and pins a CPU core for as long as KCalc is open.
At integer scaling (100%/200%) the two values are equal after one pass and the loop never starts, which is why this reads as WORKSFORME for anyone on Wayland, integer scaling, or the Qt6 high-DPI path.
Only force a resize when the shortfall exceeds the rounding error (4px). This breaks the loop on every scale factor while preserving the existing workaround that grows the window to fit its content after restoring from a maximized state (added in 6ff969e3 / d5ae89b8); those size differences are far larger than the tolerance.
Verified on the 22.12 branch (the master Qt6 build was unavailable on my test machine; the resizeEvent logic is identical): per-second CPU of the kcalc process went from a sustained 95-97% of one core to a flat 0% from the first second, with normal sizing intact.