feat: Arabic/Farsi/Urdu bidi reordering and contextual shaping — PR 1/3 (#2541)

Co-authored-by: Uri Tauber <uritaube@gmail.com>

docs/file-formats.md

@@ -90,13 +90,19 @@ if (parsedSize != fileSize) {
 
 ## `section.bin`
 
-### Version 29
+### Version 30
 
 Each file in `sections/*.bin` stores one laid-out spine section. The header is
 also the cache-busting key: if any layout-affecting setting differs from the
 current reader settings, the section is discarded and rebuilt.
 
-Version 29 includes:
+Version 30 is binary-identical to version 29. The version was bumped because
+Arabic contextual shaping changed text measurement (`getTextAdvanceX` now
+measures the shaped visual text), so word positions cached by v29 no longer
+match what `drawText` renders.
+
+Version 28 introduced serialized word style bits for underline, strikethrough,
+superscript, and subscript. The format also includes:
 
 - cache-busting fields for paragraph alignment, hyphenation, embedded CSS,
   image rendering mode, and Focus Reading
@@ -119,7 +125,7 @@ import std.mem;
 import std.string;
 import std.core;
 
-#define EXPECTED_VERSION 29
+#define EXPECTED_VERSION 30
 #define MAX_STRING_LENGTH 65535
 #define FOOTNOTE_NUMBER_LEN 32
 #define FOOTNOTE_HREF_LEN 96