Add FreeInkBook EPUB engine migration guide

Document migration plan from CrossPoint's lib/Epub to FreeInkBook, a memory-efficient clean-room EPUB engine. Covers advantages (O(paragraph+page) memory via SAX parsing, arena allocation, host-testable, full UAX#14 typography, runtime TTF/OTF support), 9-step migration strategy, ESP32-C3 constraints, and integration approach preserving existing UI layer while replacing parsing/layout stack.

test/cpfont_adapter/CMakeLists.txt

@@ -0,0 +1,34 @@
+# CpFontAdapter binds .cpfont metrics to FreeInkBook's RenderFont interface;
+# the suite needs the engine's freestanding headers. Prefer the submodule;
+# fall back to the sibling working checkout while the submodule pin predates
+# libs/book (drop the fallback once the pin advances).
+set(FREEINK_BOOK_INCLUDE "${REPO_ROOT}/freeink-sdk/libs/book/FreeInkBook/include")
+if(NOT EXISTS "${FREEINK_BOOK_INCLUDE}")
+  set(FREEINK_BOOK_INCLUDE "$ENV{HOME}/GitHub/freeink-sdk/libs/book/FreeInkBook/include")
+endif()
+
+if(NOT EXISTS "${FREEINK_BOOK_INCLUDE}")
+  message(WARNING "FreeInkBook headers not found - skipping CpFontAdapterTest")
+else()
+  add_executable(CpFontAdapterTest
+    CpFontAdapterTest.cpp
+    ${REPO_ROOT}/src/activities/reader/CpFontAdapter.cpp
+    ${REPO_ROOT}/lib/EpdFont/EpdFont.cpp
+    ${REPO_ROOT}/lib/EpdFont/EpdFontFamily.cpp
+    ${REPO_ROOT}/lib/Utf8/Utf8.cpp
+  )
+
+  target_include_directories(CpFontAdapterTest PRIVATE
+    ${REPO_ROOT}/src/activities/reader
+    ${REPO_ROOT}/lib/EpdFont
+    ${REPO_ROOT}/lib/Utf8
+    ${FREEINK_BOOK_INCLUDE}
+  )
+
+  target_link_libraries(CpFontAdapterTest PRIVATE
+    crosspoint_test_common
+    GTest::gtest_main
+  )
+
+  gtest_discover_tests(CpFontAdapterTest)
+endif()