feat(dictionary): add Hachidori backend support

- Add backend selection, setup gating, Anki integration, and external host support
- Add launcher flags, documentation, packaging, and focused tests
- Open on-demand overlay modals on the first attempt

vendor/hachidori/wasm/avif/CMakeLists.txt

@@ -0,0 +1,47 @@
+cmake_minimum_required(VERSION 3.31)
+
+project(hachidori_avif LANGUAGES C)
+
+include(FetchContent)
+
+set(BUILD_SHARED_LIBS OFF CACHE BOOL "" FORCE)
+set(AVIF_CODEC_AOM LOCAL CACHE STRING "" FORCE)
+set(AVIF_CODEC_AOM_DECODE OFF CACHE BOOL "" FORCE)
+set(AVIF_CODEC_AOM_ENCODE ON CACHE BOOL "" FORCE)
+set(AVIF_LIBYUV OFF CACHE BOOL "" FORCE)
+set(AVIF_LIBSHARPYUV OFF CACHE BOOL "" FORCE)
+set(AVIF_JPEG OFF CACHE BOOL "" FORCE)
+set(AVIF_ZLIBPNG OFF CACHE BOOL "" FORCE)
+set(AVIF_BUILD_APPS OFF CACHE BOOL "" FORCE)
+set(AVIF_BUILD_TESTS OFF CACHE BOOL "" FORCE)
+set(AOM_TARGET_CPU generic CACHE STRING "" FORCE)
+set(CONFIG_RUNTIME_CPU_DETECT 0 CACHE STRING "" FORCE)
+
+FetchContent_Declare(
+  libavif
+  GIT_REPOSITORY https://github.com/AOMediaCodec/libavif.git
+  GIT_TAG 1aadfad932c98c069a1204261b1856f81f3bc199
+  GIT_SHALLOW FALSE
+)
+FetchContent_MakeAvailable(libavif)
+
+add_executable(hachidori_avif encoder.c)
+set_target_properties(hachidori_avif PROPERTIES OUTPUT_NAME avif-encoder SUFFIX ".mjs")
+target_compile_features(hachidori_avif PRIVATE c_std_11)
+target_compile_options(hachidori_avif PRIVATE -Oz)
+target_link_libraries(hachidori_avif PRIVATE avif)
+target_link_options(hachidori_avif PRIVATE
+  -Oz
+  -sMODULARIZE=1
+  -sEXPORT_ES6=1
+  -sEXPORT_NAME=createAvifEncoderModule
+  -sENVIRONMENT=worker,node
+  -sALLOW_MEMORY_GROWTH=1
+  -sINITIAL_MEMORY=32MB
+  -sMAXIMUM_MEMORY=256MB
+  -sSTACK_SIZE=1MB
+  -sFILESYSTEM=0
+  -sMALLOC=emmalloc
+  -sEXPORTED_FUNCTIONS=_malloc,_free,_hda_create,_hda_add_rgba,_hda_finish,_hda_output,_hda_output_size,_hda_last_error,_hda_destroy
+  -sEXPORTED_RUNTIME_METHODS=HEAPU8,UTF8ToString
+)