patches: fold line index + remove NS_AX_TEXT_CAP into 0001-0002

- 0001: remove NS_AX_TEXT_CAP (100K char cap), add lineStartOffsets/
  lineCount ivars and method declarations to nsterm.h
- 0002: add lineForAXIndex:/rangeForLine: O(log L) helpers, build line
  index in ensureTextCache, replace O(L) line scanning in
  accessibilityInsertionPointLineNumber/accessibilityLineForIndex/
  accessibilityRangeForLine, free index in invalidateTextCache/dealloc
- 0009 deleted (folded into 0001+0002)
- README.txt: remove NS_AX_TEXT_CAP references, update known
  limitations, stress test threshold 50K lines

patches/README.txt

@@ -326,9 +326,12 @@ TEXT CACHE AND VISIBLE RUNS
   narrowing/widening is detected by comparing cachedTextStart
   against BUF_BEGV — these operations change the visible region
   without bumping either modiff counter.  The cache is also
-  invalidated when the window tree is rebuilt.  NS_AX_TEXT_CAP = 100,000
-  UTF-16 units (~200 KB) caps total exposure; buffers larger than
-  ~50,000 lines are truncated for accessibility purposes.
+  invalidated when the window tree is rebuilt.
+
+  There is no character cap on the accessibility text.  The entire
+  visible (non-invisible) buffer content is exposed to VoiceOver.
+  Users who do not need accessibility can set ns-accessibility-enabled
+  to nil for zero overhead.
 
   A lineStartOffsets array is built during each cache rebuild,
   recording the AX string index where each line begins.  This
@@ -651,14 +654,9 @@ KNOWN LIMITATIONS
     produce incomplete or garbled accessibility text.
 
   - Line counting (accessibilityInsertionPointLineNumber,
-    accessibilityLineForIndex:) was O(lines) in patches 1-5.
-    Patch 0009 adds a precomputed lineStartOffsets array built
-    once per cache rebuild; queries are now O(log L) via binary
-    search.
-
-  - Buffers larger than NS_AX_TEXT_CAP (100,000 UTF-16 units) are
-    truncated.  The truncation is silent; AT tools navigating past the
-    truncation boundary may behave unexpectedly.
+    accessibilityLineForIndex:) uses a precomputed lineStartOffsets
+    array built once per cache rebuild.  Queries are O(log L) via
+    binary search.
 
   - No multi-frame coordination.  EmacsView.accessibilityElements is
     per-view; there is no cross-frame notification ordering.
@@ -752,7 +750,7 @@ TESTING CHECKLIST
         *Completions*, Tab to a candidate, Enter to execute, then
         C-x o to switch windows.  Emacs must not hang.
 
-  Stress test (patch 0009 line index):
+  Stress test (line index):
     25. Open a large file (>50,000 lines).  Navigate to the end with
         M-> or C-v repeatedly.  VoiceOver speech should remain fluid
         at all positions (no progressive slowdown).