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/build.sh

@@ -0,0 +1,21 @@
+#!/bin/sh
+# Build the pinned libavif/libaom sequence encoder used by the capture worker.
+set -e
+
+AVIF_DIR=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
+WASM_DIR=$(CDPATH= cd -- "$AVIF_DIR/.." && pwd)
+REPO_ROOT=$(CDPATH= cd -- "$WASM_DIR/.." && pwd)
+AVIF_BUILD_DIR="${AVIF_BUILD_DIR:-$AVIF_DIR/build}"
+VENDOR_DIR="$REPO_ROOT/extension/vendor"
+
+# shellcheck disable=SC1091
+. "$WASM_DIR/env.sh"
+
+emcmake cmake -S "$AVIF_DIR" -B "$AVIF_BUILD_DIR" -G Ninja -DCMAKE_BUILD_TYPE=MinSizeRel
+cmake --build "$AVIF_BUILD_DIR" --parallel "$(nproc 2>/dev/null || printf '%s\n' 4)"
+
+mkdir -p "$VENDOR_DIR"
+cp "$AVIF_BUILD_DIR/avif-encoder.mjs" "$VENDOR_DIR/avif-encoder.mjs"
+cp "$AVIF_BUILD_DIR/avif-encoder.wasm" "$VENDOR_DIR/avif-encoder.wasm"
+chmod 644 "$VENDOR_DIR/avif-encoder.mjs" "$VENDOR_DIR/avif-encoder.wasm"
+ls -l "$VENDOR_DIR/avif-encoder.mjs" "$VENDOR_DIR/avif-encoder.wasm"