Refuse silent COMPOUNDCURVE chord flatten (ticket 30)

[grootstebozewolf]

CRV-CC ticket 30: COMPOUNDCURVE flatten-elimination. Off JTS #7 / feature/sfa-curve-rgr. Base is feature/zoo.

SQL/MM COMPOUNDCURVE (ISO/IEC 13249-3 §4.2.13 / §7.10.1, WKB 9) stays a COMPOUNDCURVE. Silent chord Flatten for overlay / TestBuilder consume is a refuse. Named linear fallback stays named: toLinear / Linearize / OverlayNGCurve APPROX with isApproximate()=true.

Flatten sites found

Verified the wayfinder hypothesis; discarded the parts that were already honest.

Site	Verdict	Action
OverlayNGCurve R1.7 / R-LL / R-AA / OverlayNGCircle CompoundCurve kits	Already exact; keep type	No kit rewrite
OverlayNGCurve leftover cells (unnamed)	Densify via R2	Already isApproximate()=true + CurveOps.linearise warn. Test pins it.
Stock OverlayNG / OverlayNGRobust	Silent getCoordinates() / LineString extract of CompoundCurve and CC-shelled CurvePolygon	Refuse (SqlMmTypes.refuseCompoundCurveChord)
TestBuilder OverlayNGTest.*	Raw inspect of control polygon	Refuse CompoundCurve / CC shell. CircularString CurvePolygon stays raw (sibling leftover).
TestBuilder Appium OverlayNGTest.unionIntSymDiff.half-moon.pr7	Would have Exec'd inspect on a CC shell	Fail closed: skip the dishonest Exec; pin unionIntSymDiff refuse
TestBuilder OverlayNGFunctions / linearizeForOps	Named toLinear but no warn	Stamp CurveLinearizationStrategy.warnLinearized
MoveTool / GeometryVertexMover	Already keeps members	Pin with MoveTool basics test
Hull / H-CC	Already linearizeForHull / CurveExact; leftover of locationtech#424	HOLD. Do not remint 424-b.
I/O refuseFlatten / IoFlattenHonesty	Type identity, not op honesty	Not this leftover. No type-9 reader PR.

Patches

• SqlMmTypes.refuseCompoundCurveChord — type-name walk (WKB 9) plus CurvePolygon structural-ring reflect so core does not depend on jts-curve. Public accessors first; declared walk as fallback.
• OverlayNG.getResult + EdgeNodingBuilder.add call the refuse.
• OverlayNGRobust rethrows IllegalArgumentException — a refuse is not a noding failure to snap-round.
• OverlayNGTestFunctions refuses CompoundCurve consume.
• CurveFunctions.linearize warns (named toLinear).
• CompoundCurve javadoc cites 13249-3, not 19125-2.
• Appium OverlayNGTest/unionIntSymDiff.half-moon.pr7.json skipped; playback treats an OverlayNGTest refuse as a named miss.

Tests run

jts-app included this leftover. GitHub CI build-and-test is green on 93be9ddb (4/4 checks).

• jts-core: SqlMmTypesTest 5, OverlayNGTest 52, OverlayNGRobustTest 7, OverlayNGEmptyDisjointTest 12 — 76 PASS
• jts-curve: OverlayNGCurveCompoundCurveFlattenHonestyTest 5, CompoundCurveShellOverlayTest 28, SqlMm13249CurveSpecTest 24 (SQL/MM ISO/IEC 13249-3 curve types: close remaining spec gaps #130, no regress), IoFlattenHonestyTest 8, OverlayNGCurve kit suite 52 — PASS
• jts-app leftover suite: OverlayNGTestFunctionsCompoundCurveFlattenTest 5, CurveFunctionsCompoundCurveFlattenTest 2, CompoundCurveMoveToolBasicsTest 2, OverlayStaticCurveTest 15 (CircularString inspect stays raw), HullFunctionsCurveTest 12, IOUtilFlattenHonestyTest 3, TbAppiumPr7PlaybackTest 1, TbAppiumSequenceContractTest 4 — PASS

Earlier CI reds on cc3a4280 / bb6ca330 were the fake CurvePolygon core stand-in and the half-moon OverlayNG inspect Exec. Both are closed on this head.

HOLDs refused (explicit)

• Do not remint 424-b / H-CC hull (stays tracker 424 / JTS [visual-qa] H-CC · h-cc-1 #6).
• Do not remint 508-* / 615-b / LECFlattenRow / nested-CC splice.
• JTS P2.5.5 OverlayNG-for-circles (Option B contract, OV-P2 / Bar 2) #27 OverlayNG-for-circles — OUT.
• JTS P2.5.7 package-private curve DCEL (Option C, OV-P2 / Bar 2) #38 curve DCEL public / merge into SFA/SQL-MM curve awareness: Curve rename, arc-aware operations, OverlayNGCurve ratchet (#1195 RGR series) #7 — OUT. No public noder.
• No second CompoundCurve type. No GEO-TIN 15–17. No clothoid Zenodo. No Koc railway-as-SQL/MM.
• No Year-2 ExactEllipticalArc / ExactCubicBezier / ExactClothoid / ExactNurbsSegment.
• Do not grow ExactCurve. Do not make SegmentString non-linear in core. Do not rename OverlayNGCurve → Curved. Do not walk SHARED_SNAPPED_RAY. Do not start 74-file N-SS. Do not remint ADR-0004.
• I/O type identity is not this leftover. No type-9 reader PR.
• PR SQL/MM ISO/IEC 13249-3 curve types: close remaining spec gaps #130 SQL/MM validity is already on feature/zoo; do not regress it.

This is off #7, on feature/zoo. Do not merge into PR #7 / feature/sfa-curve-rgr. Do not target master.