patches: review pass 4 - fix BUF_MODIFF->BUF_CHARS_MODIFF in P0007

P0007 (announce overlay candidates) incorrectly changed ensureTextCache
to use BUF_MODIFF, causing O(buffer-size) AX text rebuilds on every
font-lock pass.  Reverted to BUF_CHARS_MODIFF throughout.

P0008 (child frame) now cleanly adds only new functionality without
re-introducing BUF_OVERLAY_MODIFF or BUF_MODIFF.

All review blockers and major issues addressed:
- P0000: unbind_to on fall-through path
- P0001: block_input in ns_ax_buffer_text
- P0003: block_input in postCompletionAnnouncementForBuffer; [trims release]
- P0004: block_input in ns_ax_scan_interactive_spans; mojibake ---
- P0006: texinfo semicolons -> periods
- P0007: BUF_CHARS_MODIFF throughout ensureTextCache (no oscillation)
- P0008: childFrameLastBuffer=BVAR(b,name); no BUF_OVERLAY_MODIFF in
  ensureTextCache; voiceoverSetPoint init; cachedOverlayModiffForText removed

git am passes all 9 patches on Linux git 2.43.0.

patches/0007-ns-announce-overlay-completion-candidates-for-VoiceO.patch

@@ -1,4 +1,4 @@
-From 92aec64d791200f54fcd756b5a07581a6c15d0cb Mon Sep 17 00:00:00 2001
+From c1fa92dbf8caa6faffed7a0813c92bed2f983092 Mon Sep 17 00:00:00 2001
 From: Daneel <daneel@sukany.cz>
 Date: Mon, 2 Mar 2026 18:39:46 +0100
 Subject: [PATCH 7/8] ns: announce overlay completion candidates for VoiceOver
@@ -18,8 +18,8 @@ ValueChanged; keep overlay_modiff out of ensureTextCache to prevent a
 race where an AX query consumes the change before notification.
 ---
  src/nsterm.h |   1 +
- src/nsterm.m | 324 ++++++++++++++++++++++++++++++++++++++++++++-------
- 2 files changed, 286 insertions(+), 39 deletions(-)
+ src/nsterm.m | 318 +++++++++++++++++++++++++++++++++++++++++++++------
+ 2 files changed, 283 insertions(+), 36 deletions(-)
 
 diff --git a/src/nsterm.h b/src/nsterm.h
 index 5746e9e9bd..21a93bc799 100644
@@ -34,7 +34,7 @@ index 5746e9e9bd..21a93bc799 100644
  @property (nonatomic, assign) BOOL cachedMarkActive;
  @property (nonatomic, copy) NSString *cachedCompletionAnnouncement;
 diff --git a/src/nsterm.m b/src/nsterm.m
-index 8a1bfd9eb1..7fa28222b6 100644
+index 8a1bfd9eb1..523f79d235 100644
 --- a/src/nsterm.m
 +++ b/src/nsterm.m
 @@ -7263,11 +7263,154 @@ Accessibility virtual elements (macOS / Cocoa only)
@@ -228,7 +228,7 @@ index 8a1bfd9eb1..7fa28222b6 100644
       write section at the end needs synchronization to protect
       against concurrent reads from AX server thread.  */
    eassert ([NSThread isMainThread]);
-@@ -8005,25 +8149,16 @@ - (void)ensureTextCache
+@@ -8005,24 +8149,15 @@ - (void)ensureTextCache
    if (!b)
      return;
  
@@ -247,30 +247,18 @@ index 8a1bfd9eb1..7fa28222b6 100644
 -     explicit announcements in postAccessibilityNotificationsForFrame).
 -     Including overlay_modiff would silently update cachedOverlayModiff
 -     and prevent the notification dispatch from detecting changes.  */
--  ptrdiff_t chars_modiff = BUF_CHARS_MODIFF (b);
-+  ptrdiff_t modiff = BUF_MODIFF (b);
+   ptrdiff_t chars_modiff = BUF_CHARS_MODIFF (b);
    ptrdiff_t pt = BUF_PT (b);
    NSUInteger textLen = cachedText ? [cachedText length] : 0;
--  if (cachedText && cachedTextModiff == chars_modiff
 +  /* Cache validity: track BUF_MODIFF and buffer narrowing.
 +     Do NOT track BUF_OVERLAY_MODIFF here --- overlay text is not
 +     included in the cached AX text (it is handled separately via
 +     explicit announcements).  Including overlay_modiff would
 +     silently update cachedOverlayModiff and prevent the
 +     notification dispatch from detecting overlay changes.  */
-+  if (cachedText && cachedTextModiff == modiff
+   if (cachedText && cachedTextModiff == chars_modiff
        && cachedTextStart == BUF_BEGV (b)
        && pt >= cachedTextStart
-       && (textLen == 0
-@@ -8039,7 +8174,7 @@ included in the cached AX text (it is handled separately via
-     {
-       [cachedText release];
-       cachedText = [text retain];
--      cachedTextModiff = chars_modiff;
-+      cachedTextModiff = modiff;
-       cachedTextStart = start;
- 
-       if (visibleRuns)
 @@ -8108,7 +8243,7 @@ - (NSUInteger)accessibilityIndexForCharpos:(ptrdiff_t)charpos
    /* Binary search: runs are sorted by charpos (ascending).  Find the
       run whose [charpos, charpos+length) range contains the target,