R5.6: ElyShow right-click menus, PowerPoint-style; Impress table borders drag; R3 PASS

The canvas offers Ely's menu by target: slide (layouts, comment), text
(bullets, numbering, comment), shape or text box, picture (replace,
crop), table (insert, delete, merge), each item gated by the kernel's
state for its own command. Impress's table borders read as text and
drag through R5.3's path; patch 0047 reports every edge's bounds and
makes the left edge drag. A line past its bound never moves against
the drag, so a still press sends nothing.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/compatibility.md

@@ -3,7 +3,7 @@
 随发行说明发布，每个版本一份。支持某格式不等于支持它的全部功能；下表只写已验证的内容、已知限制与保存行为。
 
 版本：Ely Office 0.1.3（首版六个应用：ElyDoc、ElyTable、ElyShow、ElyPDF、ElyTree、ElyMark）。日期 2026-10-11。
-内核：LibreOffice 26.2.6.3（8221e31，加 `patches/libreoffice` 0001–0046）；MuPDF 1.28.5（8ad45e9，加 `patches/mupdf` 0001–0005）；Git 2.56.0（a018953）与 git-lfs 3.8.0。
+内核：LibreOffice 26.2.6.3（8221e31，加 `patches/libreoffice` 0001–0047）；MuPDF 1.28.5（8ad45e9，加 `patches/mupdf` 0001–0005）；Git 2.56.0（a018953）与 git-lfs 3.8.0。
 验证机：macOS 27.0 arm64。Windows 与 Linux 未验证。本机没有 Microsoft Office：与 Office 的交叉检查未做（待做）。
 
 ## 往返验证