Address Gadfly findings on #76

- clampTo's doc justified itself by stopping hexCenters "looping forever",
  which stopped being true when hexCenters became count-bounded. Say what it
  actually does now, and note the inversion the new guard relies on.
- Trim the changelog prose from hexCenters' doc down to the one line that
  earns its keep: don't re-anchor at the min corner, and why.
- Rename a test local from `max` so it stops shadowing the builtin.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01H3zbym8Doka2d7D48maSgZ

internal/service/ops_test.go

@@ -103,14 +103,14 @@ func TestHexCentersEdgeInset(t *testing.T) {
 
 			// A clump may cross the edge, but only by the half-spacing the rule
 			// allows — never enough to be mostly out in the path.
-			max := tc.spacing / 2
+			budget := tc.spacing / 2
 			for _, p := range pts {
 				over := math.Max(
 					math.Max(r.MinX-(p.x-tc.radius), (p.x+tc.radius)-r.MaxX),
 					math.Max(r.MinY-(p.y-tc.radius), (p.y+tc.radius)-r.MaxY),
 				)
-				if over > max+1e-6 {
-					t.Errorf("plop at (%.1f,%.1f) overhangs by %.2f, max %.2f", p.x, p.y, over, max)
+				if over > budget+1e-6 {
+					t.Errorf("plop at (%.1f,%.1f) overhangs by %.2f, budget %.2f", p.x, p.y, over, budget)
 				}
 			}