fix(com): hatch islands on a live seat — typed edges become temporary entities

hatch_add_boundary was refused on COM (hatch_edge_paths), so a transverse
section of any hollow part — a bushing, a flange bore — could not be drawn in
AutoCAD at all: draw_prims asked the capability map and refused up front.

ActiveX takes a loop as whole objects, which is not the same as "cannot take a
typed edge": each edge now becomes a real temporary LINE, true ARC or ELLIPSE
in the hatch's own space, appended with AppendInnerLoop, evaluated and
deleted. A loop that is only chained lines becomes one closed polyline — one
COM call instead of 180 for a flattened bore. The edge list is validated in
full first with the headless engine's messages; a loop AutoCAD refuses is
taken back out with its temporaries.

Measured on AutoCAD 2026 (25.1s), in scratch documents closed unsaved:
- a two-arc island leaves exactly 10000 - 100*pi (9685.8407) of a 100 x 100 hatch;
- the OD40/ID20 sleeve's transverse section B-B, drawn through the view engine
  and draw_prims, hatches 942.2864 mm2 — the engine's declared 180-gon;
- an open chain is refused (E_FAIL) and the entity count is unchanged.

hatch_edge_paths is now supported on both engines.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FKFStjEFzpGyLq5bMpWxTd

server.py

@@ -1859,12 +1859,15 @@ async def hatch_add_boundary(
     ],
     ctx: Context = None,
 ) -> dict:
-    """Add one boundary path built from typed edges.
+    """Add one boundary path built from typed edges - an island inside the hatch.
 
     Typed edges exist because a boundary that only accepts vertex lists
     silently straightens every curve it is given. Every edge is validated
     before any is written, so a malformed list refuses instead of leaving a
-    half-built path.
+    half-built path. Both engines: headlessly the edges become an edge path;
+    on a live seat each becomes a temporary LINE, true ARC or ELLIPSE appended
+    as an inner loop and then deleted (a chain of lines becomes one polyline).
+    A loop that does not close is refused by AutoCAD and nothing is added.
     """
     return await _backend(ctx).hatch_add_boundary(handle, edges)