Strip the bash-bin compatibility layer from Menu.qml

With bin/omarchy-menu gone there's no caller that summons the menu by
writing a JSON tempfile and polling a done file. Drop everything that
existed only to support that handshake:

  - menuJsonFile / menuJsonFileView / loadMenuJson / openMenu(json,...)
  - pendingSelectionFile / pendingDoneFile / selectionFile / doneFile
  - mergeProviderJson (the JSON-wrapper for provider output)
  - applyProc / releaseProc / doneFilesToRelease / finishDoneFile /
    releaseNextDoneFile / resetRequest / requestActive / closeMenu
  - the menuBin property pointing at the deleted bin

applySelected is now four lines (close + execDetached); cancel is two
(close + clear filter). open() takes either {menu: id} or a bare initial
menu name, and hands off to openExistingMenu which uses the cached items
from the JSONC FileViews.

Net: 91 lines smaller, no perf change.

default/quickshell/omarchy-shell/plugins/README.md

@@ -76,9 +76,12 @@ The menu definition lives outside the shell host code:
 - defaults: `default/omarchy/omarchy-menu.jsonc`
 - user extensions: `~/.config/omarchy/extensions/omarchy-menu.jsonc`
 
-`bin/omarchy-menu` still owns the Bash action helpers and dynamic providers;
-it builds the menu JSON, summons `omarchy.menu`, waits for the selection, and
-runs the selected action.
+The shell parses both JSONC files at startup (with `watchChanges: true`
+so edits take effect without a restart), evaluates `when:` / `checked:`
+bash expressions in a single batched subprocess, and executes the
+selected `action:` string directly via `Quickshell.execDetached`. The
+long-running shell process keeps the parsed menu in memory, so the
+keybind → IPC → visible path costs ~30ms cold.
 
 ## Coming soon