Flow: right-click menus like SaraFem's

Boxes, arrow labels and the background each get a menu (edit, delete,
connect, test a file, copy path/patterns, ...), using SaraFem's single
shared ContextMenu opened from _RequestMenu. Tools can open on the tester
for a given input.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

README.md

@@ -18,6 +18,10 @@ Needs SaraSortd **7.1** or newer for arrows with their own patterns (per-entry `
   as a template. A rule other inputs use too is split when you change it, so only this arrow changes.
   The bin on a box deletes the directory from SaraSortd: it leaves GlobalConf.toml and other outputs'
   rules, and its config and history files are deleted. The folder and its files stay.
+  **Right-click** works like in SaraFem, in or out of edit mode. A box: Details, Connect From Here, Edit
+  Config, Test a File, Make It an Input/Output Too, Open Folder, Copy Path, Delete. An arrow's label: Show
+  Patterns, Edit Rules, Add Patterns, Copy Patterns, Save as Template, Edit Output Config, Remove Arrow.
+  The background: Add Directory, Edit Mode, Tidy Layout, Reload.
 - **Service**: running/stopped, start/stop/restart, start on login, SaraSortd's version (and the
   SaraSuite install it came from), and its logs: its own log files or the systemd journal.
 - **Configs**: `GlobalConf.toml`, the two templates and every directory's own config, as a form (with