Prevent refine() from looping forever on near-cocircular points

[spokodev]

refine() can loop forever on a class of valid, simple polygons, hanging the calling thread.

const vertices = [
  127.65906365022843, 9.336137742499535, 124.21725103117963, 30.888097161477972,
  91.35514946628345, 89.65621376119454, 40.10446780041529, 121.5550560957686,
  -110.83205604043928, 64.03323632184248, -127.20394987965459, -14.253249980770189,
  61.074962259031416, -112.48932831632469, 127.37846573978545, -12.598669206638515,
  127.77010311801033, -7.668164657400608];
const triangles = earcut(vertices);
refine(triangles, vertices); // never returns

Cause

refine() runs a Lawson edge-flip cascade whose flip decision uses a an inexact floating-point inCircle. On near-cocircular points the test is not transitive: an edge and its flipped counterpart can both test as illegal, so a legalized edge gets re-queued and flipped back, and the cascade cycles forever. The loop has no bound. Measured incidence is about 0.5 percent of random convex float polygons (roughly 1 in 200), and exact-tie cocircular inputs do not trigger it, so it has gone unnoticed. refine is a documented public API whose docstring says the worst case is a not-quite-Delaunay edge, so a hang is the one outcome it should never produce.

Fix

Bound the cascade with a flip budget of 25 * n (n is the half-edge count, 3 times the triangle count). A converging Delaunay cascade needs O(triangles) flips in practice, so this never truncates legitimate work, while it always breaks a float-induced cycle. On hitting the cap the output is exactly what the docstring already allows: a valid manifold mesh with at worst a few not-quite-Delaunay edges (the flip itself is unchanged and convexity-guarded).

Testing

Added a test with the reproducer polygon above. On the current code the test never returns (a synchronous infinite loop freezes the whole test runner). With the fix it passes: the mesh is unchanged in size and its deviation is 0. Full suite stays green (247 tests), eslint and tsc clean. The existing refine quality tests, including the mvt-fixture perimeter-reduction check, are unaffected.