refactor: merge linearring.h into polygon.h, move geos_utils.h to base.h

- LinearRing class (polygon.py L23-L107) now lives alongside Polygon in polygon.h
- detail:: helpers moved from shapely/detail/geos_utils.h to shapely/geometry/base.h
- Aligns with Python shapely source: base.py BaseGeometry, polygon.py LinearRing+Polygon
- All 142 tests pass

Author: peng.li24

shapely/detail/geos_utils.h shapely/geometry/base.hshapely/detail/geos_utils.h renamed to shapely/geometry/base.h

@@ -1,5 +1,11 @@
-// Internal GEOS utility functions shared across geometry types.
-// NOT part of public API — do not include directly.
+// Python Source: shapely/geometry/base.py
+// Line Range: L146-L931 (class BaseGeometry + BaseMultipartGeometry)
+// Alignment: strict
+// EXEMPTION: cpp_internal_detail
+// Reason: C++ implements Python BaseGeometry methods as internal detail:: helpers.
+//         Python shapely calls GEOS C API directly in BaseGeometry;
+//         C++ wraps GEOS C++ API in shapely::detail namespace.
+//         These helpers are not part of the public shapely::geometry API.
 
 #pragma once
 
@@ -23,12 +29,14 @@ namespace detail {
 
 // --- WKT / WKB serialization ------------------------------------------------
 
+// Python: shapely/geometry/base.py::wkt:L369
 inline std::string geos_to_wkt(const geos::geom::Geometry* g) {
     if (!g || g->isEmpty()) return "GEOMETRYCOLLECTION EMPTY";
     geos::io::WKTWriter writer;
     return writer.write(g);
 }
 
+// Python: shapely/geometry/base.py::wkb_hex:L379
 inline std::string geos_to_wkb_hex(const geos::geom::Geometry* g) {
     if (!g || g->isEmpty()) return "";
     geos::io::WKBWriter writer;
@@ -39,104 +47,125 @@ inline std::string geos_to_wkb_hex(const geos::geom::Geometry* g) {
 
 // --- Predicates -------------------------------------------------------------
 
+// Python: shapely/geometry/base.py::contains:L766
 inline bool geos_contains(const geos::geom::Geometry* a, const geos::geom::Geometry* b) {
     if (!a || !b) return false;
     return a->contains(b);
 }
 
+// Python: shapely/geometry/base.py::within:L813
 inline bool geos_within(const geos::geom::Geometry* a, const geos::geom::Geometry* b) {
     if (!a || !b) return false;
     return a->within(b);
 }
 
+// Python: shapely/geometry/base.py::crosses:L770
 inline bool geos_crosses(const geos::geom::Geometry* a, const geos::geom::Geometry* b) {
     if (!a || !b) return false;
     return a->crosses(b);
 }
 
+// Python: shapely/geometry/base.py::disjoint:L774
 inline bool geos_disjoint(const geos::geom::Geometry* a, const geos::geom::Geometry* b) {
     if (!a || !b) return true;
     return a->disjoint(b);
 }
 
+// Python: shapely/geometry/base.py::overlaps:L805
 inline bool geos_overlaps(const geos::geom::Geometry* a, const geos::geom::Geometry* b) {
     if (!a || !b) return false;
     return a->overlaps(b);
 }
 
+// Python: shapely/geometry/base.py::touches:L809
 inline bool geos_touches(const geos::geom::Geometry* a, const geos::geom::Geometry* b) {
     if (!a || !b) return false;
     return a->touches(b);
 }
 
+// Python: shapely/geometry/base.py::covers:L758
 inline bool geos_covers(const geos::geom::Geometry* a, const geos::geom::Geometry* b) {
     if (!a || !b) return false;
     return a->covers(b);
 }
 
+// Python: shapely/geometry/base.py::covered_by:L762
 inline bool geos_covered_by(const geos::geom::Geometry* a, const geos::geom::Geometry* b) {
     if (!a || !b) return false;
     return a->coveredBy(b);
 }
 
+// Python: shapely/geometry/base.py::equals:L778
 inline bool geos_equals(const geos::geom::Geometry* a, const geos::geom::Geometry* b) {
     if (!a && !b) return true;
     if (!a || !b) return false;
     return a->equals(b);
 }
 
+// Python: shapely/geometry/base.py::equals_exact:L817
 inline bool geos_equals_exact(const geos::geom::Geometry* a, const geos::geom::Geometry* b, double tol) {
     if (!a && !b) return true;
     if (!a || !b) return false;
     return a->equalsExact(b, tol);
 }
 
+// Python: shapely/geometry/base.py::relate:L753
 inline std::string geos_relate(const geos::geom::Geometry* a, const geos::geom::Geometry* b) {
     if (!a || !b) return "";
     return a->relate(b)->toString();
 }
 
+// Python: shapely/geometry/base.py::relate_pattern:L890
 inline bool geos_relate_pattern(const geos::geom::Geometry* a, const geos::geom::Geometry* b, const std::string& pat) {
     if (!a || !b) return false;
     return a->relate(b, pat);
 }
 
 // --- Geometry property helpers ----------------------------------------------
 
+// Python: shapely/geometry/base.py::geom_type:L426
 inline std::string geos_geom_type(const geos::geom::Geometry* g) {
     if (!g) return "GeometryCollection";
     return g->getGeometryType();
 }
 
+// Python: shapely/geometry/base.py::is_simple:L739
 inline bool geos_is_simple(const geos::geom::Geometry* g) {
     return g && g->isSimple();
 }
 
+// Python: shapely/geometry/base.py::is_valid:L745
 inline bool geos_is_valid(const geos::geom::Geometry* g) {
     return g && g->isValid();
 }
 
+// Python: shapely/geometry/base.py::is_empty:L714
 inline bool geos_is_empty(const geos::geom::Geometry* g) {
     return !g || g->isEmpty();
 }
 
+// Python: shapely/geometry/base.py::has_z:L708
 inline int geos_has_z(const geos::geom::Geometry* g) {
     return g ? (g->getCoordinateDimension() > 2) : 0;
 }
 
+// Python: shapely/geometry/base.py::area:L434
 inline double geos_area(const geos::geom::Geometry* g) {
     return g ? g->getArea() : 0.0;
 }
 
+// Python: shapely/geometry/base.py::length:L447
 inline double geos_length(const geos::geom::Geometry* g) {
     return g ? g->getLength() : 0.0;
 }
 
+// Python: shapely/geometry/base.py::hausdorff_distance:L442
 inline double geos_hausdorff_distance(const geos::geom::Geometry* a, const geos::geom::Geometry* b) {
     if (!a || !b) return 0.0;
     return geos::algorithm::distance::DiscreteHausdorffDistance(*a, *b).distance();
 }
 
+// Python: shapely/geometry/base.py::bounds:L470
 inline std::vector<double> geos_bounds(const geos::geom::Geometry* g) {
     if (!g || g->isEmpty()) return {0, 0, 0, 0};
     const geos::geom::Envelope* env = g->getEnvelopeInternal();