patches: auto-detect Zoom/VoiceOver; single variable gates both

Changes:
- EmacsApp gets ns_update_accessibility_state and
  ns_accessibility_did_change: methods (patch 0005)
- At startup: UAZoomEnabled() + AXIsProcessTrustedWithOptions()
  determine initial ns_accessibility_enabled state
- com.apple.accessibility.api distributed notification updates it
  whenever any AT connects or disconnects
- All Zoom call sites (UAZoomChangeFocus) now gated by
  ns_accessibility_enabled in addition to ns_zoom_enabled_p()
- ns-accessibility-enabled docstring updated to describe auto-detect

Result: zero config needed; zero overhead when no AT is active;
single variable overrides auto-detection when needed.

patches/0001-ns-add-accessibility-base-classes-and-text-extractio.patch

@@ -1,4 +1,4 @@
-From 92f8d65bd248ac3bcc5d40b0707ffa184d3c7fa5 Mon Sep 17 00:00:00 2001
+From 971bf8f19bec3a89144ddf2375cd17a4d95bb707 Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
 Subject: [PATCH 2/9] ns: add accessibility base classes and text extraction