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/extension/settings-dom.js

@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+const PAGE_THEMES = new WeakMap();
+
+export function applyPageTheme(document, options) {
+  let state = PAGE_THEMES.get(document);
+  if (!state) {
+    const media = document.defaultView?.matchMedia?.("(prefers-color-scheme: dark)")
+      ?? { matches: false, addEventListener() {} };
+    state = { media, theme: options.popupTheme };
+    media.addEventListener("change", () => {
+      if (state.theme === "auto") document.documentElement.dataset.hoshidictsTheme = media.matches ? "dark" : "light";
+    });
+    PAGE_THEMES.set(document, state);
+  }
+  state.theme = options.popupTheme;
+  let resolvedTheme = state.theme;
+  if (resolvedTheme === "auto") resolvedTheme = state.media.matches ? "dark" : "light";
+  document.documentElement.dataset.hoshidictsTheme = resolvedTheme;
+}
+
+const STATUS_CLASSES = {
+  working: "is-working",
+  ready: "is-ready",
+  error: "is-error",
+};
+
+export function setStatusOutput(output, message, tone) {
+  if (output.textContent !== message) output.textContent = message;
+  for (const [state, className] of Object.entries(STATUS_CLASSES)) {
+    const enabled = tone === state;
+    if (output.classList.contains(className) !== enabled) output.classList.toggle(className, enabled);
+  }
+}
+
+export function reorderSettingsRows(container, ordered) {
+  if (ordered.length === container.children.length && ordered.every((row, index) => container.children[index] === row)) return;
+  const focused = ordered.find(row => row.contains(container.ownerDocument.activeElement));
+  const focusIndex = ordered.indexOf(focused);
+  ordered.forEach((row, index) => {
+    if (focused && index < focusIndex) focused.before(row);
+    else if (row !== focused) container.append(row);
+  });
+}