P2.5.4 robustness / tangent stamp in jts-curve (OV-P2 / Bar 2)

[grootstebozewolf]

Stacked on #24 @ 41cd38a. Do not merge this into #7. This is OV-P2 / Bar 2, not OV-P1. Does not merge #12 / #13 / #15 / #16 / #17 / #18 / #19 / #20 / #23 / #24 / #7. Does not push to feature/sfa-curve-rgr or master. P2.5.5 is not started.

Sentence

The noder is the named-miss suite, one assembly rule at a time. P2.1 nodes, P2.2 overlap-as-edge, P2.3 bite vs hole, P2.4 two-hole, hole-on-diameter, P2.5.2 N-string nodes, P2.5.3 N-shell faces. This rung is near-tangent robustness (catalog: “P2.5.4 Near-tangent robustness; stop if snap-round.”). Densify is never a noder. Core SegmentString / Noder is P2.5.5, 74 files, LOCKED.

Assembly rule

Named stamp, not a HotPixel. The only new cell is HALF_DISC × HALF_HANGING × STADIUM_ODD (H-SHELL-N-ODD crossings (±1, 0) + tangent (0, 5)). hasCoincidentLeave (ANGLE_EPS = 1e-8) still stamps: two different pieces leaving at the same angle are a tangent. Ordering them is snap-rounding. faces returns null and missReason() names P2.5.4 tangent leave-angle. A local curvature order was tried and walks the wrong rings — that is not a laser. If the walk needs HotPixel / ScaledNoder / core SegmentString, stamp and stop. That is P2.5.4 done.

Not this rung (existing named nulls, unchanged):

• H-ANNULUS-TANGENT / CIRCLE_INT_TAN — P2.2 pinch
• TOUCH-ext — P2.2 kiss
• H-SHELL-N-MIXED / ON_DIAMETER — interval, not a tangent
• H-SHELL-HOLE-X / holed Geometry — P2.3/P2.4
• H-SHELL-N-ODD N=2 (HALF_DISC × STADIUM_ODD) — walk already stamps; pair-kit fallback already recovers the rings

Cells

Cell	Product
N=2 pair-kit lasers (R1.5, R1.6-2, H-SHELL-2, H-FOUR / H-SHELL-N, H-SHELL-N-ODD, H-SAME-CIRCLE)	unchanged laser; isApproximate()=false
HALF_DISC × HALF_HANGING × STADIUM_FOUR	unchanged nine faces
HALF_DISC × HALF_HANGING × STADIUM_ODD	this rung: named null P2.5.4 tangent leave-angle (snap-rounding, not a walk)

Pins

Must stay green / bit-identical where already lasering:

• N=2 faces recover pair-kit CAP+XOR (R1.5, R1.6-2, H-SHELL-2, H-FOUR / H-SHELL-N, H-SHELL-N-ODD pair-kit fallback, H-SAME-CIRCLE)
• N=3 HALF_DISC × HALF_HANGING × STADIUM_FOUR: nine named faces, union area 25.5π − LENS + 2
• P2.1–P2.5.3 pair noder results unchanged
• OverlayNGCurvePerfGateTest 82 / 0 at 15% slack

This rung's only new pin: testN3TangentStampsNull — HALF_DISC × HALF_HANGING × STADIUM_ODD is a named null with reason P2.5.4 tangent leave-angle.

What this is not

• Not P2.5.5 core SegmentString / Noder (74-file blast). No org.locationtech.jts.noding change.
• Not a merge into feature/sfa-curve-rgr / PR SFA/SQL-MM curve awareness: Curve rename, arc-aware operations, OverlayNGCurve ratchet (#1195 RGR series) #7 / locationtech master
• Not CC-NEST-ANNULUS / R1.6-honesty / H-DISC leftover overlay kits
• Not Apollonius / LEC (LEC point-site candidate completeness (NTS.Proofs 474) #22 is a different lane)
• Does not rewrite P2.1–P2.5.3 pair noder or face results that already laser
• Does not re-stamp P2.2 pinch / kiss / MIXED or P2.3/P2.4 holed
• No new public API / no N-ary overlay

Verify

mvn -pl modules/curve -am test -DfailIfNoTests=false -Dcheckstyle.skip=true -Dpmd.skip=true \
  -Dtest=CurveSegmentStringTest,CompoundCurveShellOverlayTest,CircularArcOverlayTest,CircularDiscOverlayTest,CircularDiscPolygonOverlayTest,CircularLineOverlayTest,OverlayNGCurvePhase0Test,OverlayNGCurveRatchetTest,OverlayNGCurvePerfGateTest
bash dev/check-no-curved.sh
mvn -pl modules/curve checkstyle:check
mvn -pl modules/curve pmd:check

All green after this revision:

• CurveSegmentStringTest 24 / 0 (testN3TangentStampsNull is the named near-tangent stamp; MIXED / pinch / kiss / holed / N=2 H-SHELL-N-ODD unchanged)
• CompoundCurveShellOverlayTest 27 / 0
• CircularArcOverlayTest 11 / 0
• CircularDiscOverlayTest 12 / 0
• CircularDiscPolygonOverlayTest 7 / 0
• CircularLineOverlayTest 7 / 0
• OverlayNGCurvePhase0Test 19 / 0
• OverlayNGCurveRatchetTest 50 / 0
• OverlayNGCurvePerfGateTest 82 / 0 (15% slack)
• Naming-guard OK; Checkstyle 0 violations; PMD check on jts-curve succeeded

Slack stays 15%. Overlay name is OverlayNGCurve. No new public API. No noder was written in jts-core. P2.5.5 was not started.