fix(gfx): 0x1f7 is a registry ERASE, not a create

RE correction: op 0x1f7's worker gfx_registry_erase_range (@0x47d8b0) loops
gfx_registry_erase over [handle, handle+count) — a teardown, not a create.
Objects are created lazily by the geometry SET ops (gfx_object_get_or_create).
GfxState.EraseRange + VM case + tests; opcodes.toml renamed gfx-elem-create ->
gfx-elem-erase; Ghidra handler + workers annotated. Booted SC0000 CG geometry
unchanged for the working CGs (no regression). Engine 40 green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

engine/Age.Engine.Tests/GfxStateTests.cs

@@ -38,4 +38,25 @@ public class GfxStateTests
     [Fact]
     public void PackColorPacksArgb()
         => Assert.Equal(0x80_112233L, GfxState.PackColor(0x80, 0x112233));
+
+    [Fact]
+    public void EraseRangeRemovesHandlesInRange()
+    {
+        var g = new GfxState();
+        g.GetOrCreate(0x10); g.GetOrCreate(0x11); g.GetOrCreate(0x12); g.GetOrCreate(0x20);
+        g.EraseRange(0x10, 3);                      // count>1 → erase [0x10, 0x13)
+        Assert.Equal(-1, g.QuerySlot(0x10));
+        Assert.Equal(-1, g.QuerySlot(0x12));
+        Assert.NotEqual(-1, g.QuerySlot(0x20));     // outside the range, kept
+    }
+
+    [Fact]
+    public void EraseRangeCountLeOneErasesSingleHandle()
+    {
+        var g = new GfxState();
+        g.GetOrCreate(0x10); g.GetOrCreate(0x11);
+        g.EraseRange(0x10, 1);                       // count<=1 → single handle
+        Assert.Equal(-1, g.QuerySlot(0x10));
+        Assert.NotEqual(-1, g.QuerySlot(0x11));
+    }
 }