perf: Replace std::list with std::vector in text layout (#1038)

## Summary

_Revision to @blindbat's #802. Description comes from the original PR._

- Replace `std::list` with `std::vector` for word storage in `TextBlock`
and `ParsedText`
- Use index-based access (`words[i]`) instead of iterator advancement
(`std::advance(it, n)`)
- Remove the separate `continuesVec` copy that was built from
`wordContinues` for O(1) access — now unnecessary since
`std::vector<bool>` already provides O(1) indexing

## Why

`std::list` allocates each node individually on the heap with 16 bytes
of prev/next pointer overhead per node. For text layout with many small
words, this means:
- Scattered heap allocations instead of contiguous memory
- Poor cache locality during iteration (each node can be anywhere in
memory)
- Per-node malloc/free overhead during construction and destruction

`std::vector` stores elements contiguously, giving better cache
performance during the tight rendering and layout loops. The
`extractLine` function also benefits: list splice was O(1) but required
maintaining three parallel iterators, while vector range construction
with move iterators is simpler and still efficient for the small
line-sized chunks involved.

## Files changed

- `lib/Epub/Epub/blocks/TextBlock.h` / `.cpp`
- `lib/Epub/Epub/ParsedText.h` / `.cpp`

## AI Usage

YES

## Test plan

- [ ] Open an EPUB with mixed formatting (bold, italic, underline) —
verify text renders correctly
- [ ] Open a book with justified text — verify word spacing is correct
- [ ] Open a book with hyphenation enabled — verify words break
correctly at hyphens
- [ ] Navigate through pages rapidly — verify no rendering glitches or
crashes
- [ ] Open a book with long paragraphs — verify text layout matches
pre-change behavior

---------

Co-authored-by: Kuanysh Bekkulov <kbekkulov@gmail.com>

lib/Epub/Epub/ParsedText.h

@@ -3,7 +3,6 @@
 #include <EpdFontFamily.h>
 
 #include <functional>
-#include <list>
 #include <memory>
 #include <string>
 #include <vector>
@@ -14,9 +13,9 @@
 class GfxRenderer;
 
 class ParsedText {
-  std::list<std::string> words;
-  std::list<EpdFontFamily::Style> wordStyles;
-  std::list<bool> wordContinues;  // true = word attaches to previous (no space before it)
+  std::vector<std::string> words;
+  std::vector<EpdFontFamily::Style> wordStyles;
+  std::vector<bool> wordContinues;  // true = word attaches to previous (no space before it)
   BlockStyle blockStyle;
   bool extraParagraphSpacing;
   bool hyphenationEnabled;
@@ -28,8 +27,7 @@ class ParsedText {
                                                   int spaceWidth, std::vector<uint16_t>& wordWidths,
                                                   std::vector<bool>& continuesVec);
   bool hyphenateWordAtIndex(size_t wordIndex, int availableWidth, const GfxRenderer& renderer, int fontId,
-                            std::vector<uint16_t>& wordWidths, bool allowFallbackBreaks,
-                            std::vector<bool>* continuesVec = nullptr);
+                            std::vector<uint16_t>& wordWidths, bool allowFallbackBreaks);
   void extractLine(size_t breakIndex, int pageWidth, int spaceWidth, const std::vector<uint16_t>& wordWidths,
                    const std::vector<bool>& continuesVec, const std::vector<size_t>& lineBreakIndices,
                    const std::function<void(std::shared_ptr<TextBlock>)>& processLine);