patches: address remaining medium/low review findings

M-REM-1 - Stack array bound comment:
ns_ax_selected_child_frame_text uses line_starts/line_ends[128].
Added comment documenting the 128-line bound and the 10,000-character
upstream guard that makes silent truncation safe in practice.

M-REM-2 - Remove dead BUFFER_LIVE_P check:
The second BUFFER_LIVE_P check in announceChildFrameCompletion (after
updating childFrameLastBuffer/Modiff) is unreachable: no code between
the entry check and this point can kill the buffer.  Replaced with
eassert so DEBUG builds catch violations while releasing dead code.

M-REM-3 - @interface declaration for postEchoAreaAnnouncementIfNeeded:
Added declaration to the #ifdef NS_IMPL_COCOA accessibility block in
nsterm.h alongside existing postAccessibilityUpdates and
announceChildFrameCompletion declarations.  postAccessibilityUpdates
is called from ns_update_end; all three methods should be declared.

L-REM-4 - Commit message class name:
Changed (EmacsAXBuffer) to (EmacsAccessibilityBuffer) in the subject
line.  EmacsAXBuffer does not exist; EmacsAccessibilityBuffer is the
actual class that received the voiceoverSetPoint ivar.

NEWS - Remove third-party package names:
Replaced 'Vertico, Icomplete, Ivy for overlay candidates; Corfu,
Company-box for child frame popups' with generic descriptions per GNU
Emacs NEWS convention (third-party package names avoided in NEWS).

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

@@ -1,4 +1,4 @@
-From b6f4bb85d337a22bd6e761181aa0f192d5d078f8 Mon Sep 17 00:00:00 2001
+From affdaf60d28ad4d9836c6505216e19599b31c437 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