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.go

@@ -29,7 +29,10 @@ type Region struct {
 }
 
 // clampTo intersects the region with an object's local bounds (±halfW, ±halfH),
-// so an oversized caller-supplied region can't make hexCenters loop forever.
+// so a fill can't plant outside the object it was aimed at.
+//
+// Note this INVERTS (Max ends up below Min) rather than empties a region that
+// misses the object altogether — hexCenters treats that as "nothing to plant".
 func (r Region) clampTo(halfW, halfH float64) Region {
 	return Region{
 		MinX: math.Max(r.MinX, -halfW), MinY: math.Max(r.MinY, -halfH),
@@ -187,10 +190,9 @@ type localPoint struct{ x, y float64 }
 // the edge that the rule asks for. Overhang is capped there and nowhere near the
 // full radius: a clump mostly outside the bed is a drawing of plants in the path.
 //
-// Anchoring at the min corner instead (what this did originally) was wrong twice
+// Do not "simplify" this back to anchoring at the region's min corner. That is
-// over: staggered rows started a FULL pitch in, leaving a clump-sized bare strip
+// what #75 was: staggered rows start a full pitch in, and the leftover all lands
-// down one side of every other row, while the far edge had clumps hanging off it
+// on the far edge, where clumps hang outside a bed that nothing clips them to.
-// by 13cm — and nothing clips them, so they drew outside the bed.
 func hexCenters(r Region, radius, spacing float64) []localPoint {
 	if radius <= 0 {
 		return nil

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 {
+				if over > budget+1e-6 {
-					t.Errorf("plop at (%.1f,%.1f) overhangs by %.2f, max %.2f", p.x, p.y, over, max)
+					t.Errorf("plop at (%.1f,%.1f) overhangs by %.2f, budget %.2f", p.x, p.y, over, budget)
 				}
 			}