patches: address maintainer review findings (C1/C2/H1/H2/M5/M6)

C1 - block_input ordering in ns_ax_buffer_text:
block_input() now called before record_unwind_protect_void(unblock_input).
Previously the unwind handler could have been called without a matching
block_input, corrupting the input-blocking reference count.

C2 - unbind_to missing in patch 0004:
unbind_to(blk_count, Qnil) moved from patch 0008 to patch 0004 so that
ns_ax_scan_interactive_spans has a complete block_input/unbind_to pair
when patches 0000-0004 are applied independently.

H1 - Zoom patch forward dependency on VoiceOver:
Removed forward declaration 'static bool ns_ax_face_is_selected' and
the delegation from ns_zoom_face_is_selected.  Restored standalone
implementation of ns_zoom_face_is_selected in the Zoom patch so patch
0000 compiles and links independently of the VoiceOver patches.

H2 - ns_accessibility_enabled removal undocumented:
Added comment to ns_zoom_track_completion explaining that Zoom cursor
tracking is gated only on ns_zoom_enabled_p(), not ns_accessibility_enabled.
Users running Zoom without VoiceOver must still get completion tracking.

M5 - childFrameLastBuffer GC safety undocumented:
Added comment at the assignment site explaining why BVAR(b, name) (an
interned symbol reachable from obarray) is GC-safe without staticpro.

M6 - FOR_EACH_FRAME without block_input:
Added block_input/unblock_input around the FOR_EACH_FRAME loop in
postAccessibilityUpdates that checks for visible child frames.
Vframe_list must not be modified by timers or process sentinels
during iteration.

patches/0006-doc-add-VoiceOver-accessibility-section-to-macOS-app.patch

@@ -1,4 +1,4 @@
-From b863369a4d33a3488c3fa9de0cf0eca687b40447 Mon Sep 17 00:00:00 2001
+From 7578a7b5e33557c7e34674cd0bf3b7cf627898e6 Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
 Subject: [PATCH 6/8] doc: add VoiceOver accessibility section to macOS
@@ -110,10 +110,10 @@ index 6bd334f48e..8d4a7825d8 100644
  @section GNUstep Support
  
 diff --git a/src/nsterm.m b/src/nsterm.m
-index 7c118045bd..a0598a73c2 100644
+index 32eb04acef..8e5cc7e1d7 100644
 --- a/src/nsterm.m
 +++ b/src/nsterm.m
-@@ -14709,9 +14709,13 @@ Nil means use fullscreen the old (< 10.7) way.  The old way works better with
+@@ -14710,9 +14710,13 @@ Nil means use fullscreen the old (< 10.7) way.  The old way works better with
  
    DEFVAR_BOOL ("ns-accessibility-enabled", ns_accessibility_enabled,
       doc: /* Non-nil enables Zoom cursor tracking and VoiceOver support.