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/0004-ns-add-interactive-span-elements-for-Tab-navigation.patch

@@ -1,4 +1,4 @@
-From 5d5aca0665a22d3bf3cce54e53ec58fa9defab6e Mon Sep 17 00:00:00 2001
+From 6a4b3c33a0d9fdced519aff87cc02da13763f17c Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
 Subject: [PATCH 4/8] ns: add interactive span elements for Tab navigation
@@ -14,14 +14,14 @@ elements with an AXPress action that sends a synthetic TAB keystroke.
 (accessibilityChildrenInNavigationOrder): Return cached span array,
 rebuilding lazily when interactiveSpansDirty is set.
 ---
- src/nsterm.m | 291 +++++++++++++++++++++++++++++++++++++++++++++++++++
- 1 file changed, 291 insertions(+)
+ src/nsterm.m | 292 +++++++++++++++++++++++++++++++++++++++++++++++++++
+ 1 file changed, 292 insertions(+)
 
 diff --git a/src/nsterm.m b/src/nsterm.m
-index 9e0e317237..b460beb00c 100644
+index 9e0e317237..8aa5b6ac1b 100644
 --- a/src/nsterm.m
 +++ b/src/nsterm.m
-@@ -9346,6 +9346,297 @@ - (NSRect)accessibilityFrame
+@@ -9346,6 +9346,298 @@ - (NSRect)accessibilityFrame
  
  @end
  
@@ -181,6 +181,7 @@ index 9e0e317237..b460beb00c 100644
 +      pos = span_end;
 +    }
 +
++  unbind_to (blk_count, Qnil);
 +  return [[spans copy] autorelease];
 +}
 +