patches: fix all review issues from Opus core maintainer review

BLOCKERS fixed:
- #1: add missing skip_overlay_scan: label (goto without target)
- #2: move accessibilityLineForIndex: to patch 0002 (used in 0002/0003,
  was defined in 0007 — forward reference crash risk)
- #3: move BOOL singleLineMove to patch 0008 (declared in 0007, unused
  until 0008 — -Werror build failure)

WARNINGS fixed:
- #1: block_input ordering at 5 sites (record_unwind_protect_void must
  come AFTER block_input to avoid unmatched unblock_input on error)
- #2: deduplicate ns_ax_face_is_selected (move to patch 0001, remove
  from patch 0007 where it was duplicated)
- #4: improve childFrameLastBuffer comment (document rename edge case)
- #5: complete ChangeLog for patch 0007 (add 3 missing method entries)
- #6: document lastSelectedWindow/lastRootWindow GC safety in nsterm.h

MINOR fixed:
- #2: wrap ns_zoom_track_completion call in MAC_OS_X_VERSION >= 101000
  guard (consistent with the function definition)
- #3: @cindex Zoom verified present in VoiceOver section (already OK)
- #4: raise line_starts/line_ends bound from 128 to 512 (consistent
  with ns_ax_selected_overlay_text)
- #5: add echo_area_buffer[] lifetime comment referencing xdisp.c

All 9 patches apply cleanly (git apply verified sequentially).

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

@@ -1,4 +1,4 @@
-From 23139d3e63a0d97cf1fdf0421fd7c41acce0bd6b Mon Sep 17 00:00:00 2001
+From 274c545be1a3af3c7e6f416ac3a22e3b98626b0b Mon Sep 17 00:00:00 2001
 From: Martin Sukany <martin@sukany.cz>
 Date: Sat, 28 Feb 2026 12:58:11 +0100
 Subject: [PATCH 7/9] doc: add VoiceOver accessibility section to macOS
@@ -111,10 +111,10 @@ index 6bd334f48e..72ac3a9aa9 100644
  @section GNUstep Support
  
 diff --git a/src/nsterm.m b/src/nsterm.m
-index 4ba9b41b3b..a0419bb5df 100644
+index c3cd83b774..e4e43dd7a3 100644
 --- a/src/nsterm.m
 +++ b/src/nsterm.m
-@@ -14715,9 +14715,13 @@ Nil means use fullscreen the old (< 10.7) way.  The old way works better with
+@@ -14764,9 +14764,13 @@ 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.