Add chapter select support to XTC files (#145)

## Summary

- **What is the goal of this PR?** Add chapter selection support to the
XTC reader activity, including parsing chapter metadata from XTC files.
- **What changes are included?** Implemented XTC chapter parsing and
exposure in the XTC library, added a chapter selection activity for XTC,
integrated it into XtcReaderActivity, and normalized chapter page
indices by shifting them to 0-based.

  ## Additional Context

- The reader uses 0-based page indexing (first page = 0), but the XTC
chapter table appears to be 1-based (first page = 1), so chapter
start/end pages are shifted down by 1 during parsing.

lib/Xtc/Xtc/XtcParser.h

@@ -70,6 +70,9 @@ class XtcParser {
   // Get title from metadata
   std::string getTitle() const { return m_title; }
 
+  bool hasChapters() const { return m_hasChapters; }
+  const std::vector<ChapterInfo>& getChapters() const { return m_chapters; }
+
   // Validation
   static bool isValidXtcFile(const char* filepath);
 
@@ -81,16 +84,19 @@ class XtcParser {
   bool m_isOpen;
   XtcHeader m_header;
   std::vector<PageInfo> m_pageTable;
+  std::vector<ChapterInfo> m_chapters;
   std::string m_title;
   uint16_t m_defaultWidth;
   uint16_t m_defaultHeight;
   uint8_t m_bitDepth;  // 1 = XTC/XTG (1-bit), 2 = XTCH/XTH (2-bit)
+  bool m_hasChapters;
   XtcError m_lastError;
 
   // Internal helper functions
   XtcError readHeader();
   XtcError readPageTable();
   XtcError readTitle();
+  XtcError readChapters();
 };
 
 }  // namespace xtc