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/anki-pitch.js

@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Copyright (C) 2023-2026 Yomitan Authors
+// Copyright (C) 2021-2022 Yomichan Authors
+// Graph notation follows Yomitan's pronunciation-generator.js (GPL-3.0-or-later),
+// including its Jidoujisho-style kana graph: https://github.com/yomidevs/yomitan
+import "./render/glossary.js";
+import { escapeAnkiHtml as escape } from "./anki-templates.js";
+
+function pitchContour(reading, pitch) {
+  const { splitPitchAccentMorae, buildPitchAccentMorae } = globalThis.HDGlossary;
+  if (pitch.pattern) {
+    const morae = splitPitchAccentMorae(reading);
+    // The engine stores string positions in pattern, with a placeholder numeric
+    // position of zero. Never interpret an unsupported pattern as heiban.
+    if (!morae.length || !/^[HL]+$/u.test(pitch.pattern)
+      || pitch.pattern.length < morae.length || pitch.pattern.length > morae.length + 1) return null;
+    return { morae, levels: [...pitch.pattern.padEnd(morae.length + 1, pitch.pattern.at(-1))] };
+  }
+  const morae = buildPitchAccentMorae(reading, pitch.position);
+  if (!morae) return null;
+  return { morae: morae.map(mora => mora.text),
+    levels: [...morae.map(mora => mora.level === "high" ? "H" : "L"), pitch.position === 0 ? "H" : "L"] };
+}
+
+function graphLine(from, to, radius) {
+  // Stop at the dots' edges so hollow downstep/particle marks stay transparent
+  // on both light and dark cards, without masks or document-wide SVG IDs.
+  const dx = to.x - from.x, dy = to.y - from.y;
+  const scale = radius / Math.hypot(dx, dy);
+  return `M${from.x + dx * scale} ${from.y + dy * scale}L${to.x - dx * scale} ${to.y - dy * scale}`;
+}
+
+function pitchGraph(reading, pitch, kana) {
+  const contour = pitchContour(reading, pitch);
+  if (!contour) return "";
+  const { morae, levels } = contour;
+  const step = kana ? 35 : 50, height = kana ? 80 : 100, radius = kana ? 5 : 15;
+  const highY = kana ? 10 : 25;
+  const lowY = kana ? 35 : 75;
+  const points = levels.map((level, index) => ({ x: step * (index + 0.5),
+    y: level === "H" ? highY : lowY }));
+  const width = step * points.length;
+  const label = `${reading}: pitch accent ${pitch.pattern || pitch.position}`;
+  const lines = points.slice(1).map((point, index) => {
+    const tail = index === morae.length - 1;
+    return `<path d="${graphLine(points[index], point, radius)}" fill="none" stroke="currentColor" stroke-width="${kana ? 1.5 : 5}"${tail && !kana ? ' stroke-dasharray="5 5"' : ""}/>`;
+  });
+  const dots = points.slice(0, -1).map(({ x, y }, index) => {
+    const downstep = !kana && levels[index] === "H" && levels[index + 1] === "L";
+    return `<circle class="pronunciation-graph-dot" cx="${x}" cy="${y}" r="${radius}" fill="${downstep ? "none" : "currentColor"}"${downstep ? ' stroke="currentColor" stroke-width="5"' : ""}/>`
+      + (downstep ? `<circle cx="${x}" cy="${y}" r="5" fill="currentColor"/>` : "");
+  });
+  const tail = points.at(-1);
+  const tailAttributes = `class="pronunciation-graph-tail" data-pitch="${levels.at(-1) === "H" ? "high" : "low"}" fill="none" stroke="currentColor"`;
+  // Match Yomitan's distinct particle radius so card CSS for 5-unit mora dots
+  // does not fill the hollow JJ particle.
+  const particle = kana
+    ? `<circle ${tailAttributes} cx="${tail.x}" cy="${tail.y}" r="4" stroke-width="2"/>`
+    : `<path ${tailAttributes} d="M${tail.x} ${tail.y + 13}l15 -26h-30Z" stroke-width="5"/>`;
+  const labels = kana ? morae.map((mora, index) =>
+    `<text x="${points[index].x}" y="70" text-anchor="middle"${Array.from(mora).length > 1 ? ' textLength="30" lengthAdjust="spacingAndGlyphs"' : ""} style="font: 20px sans-serif; fill: currentColor;">${escape(mora)}</text>`).join("") : "";
+  return `<svg xmlns="http://www.w3.org/2000/svg" class="pronunciation-graph" viewBox="0 0 ${width} ${height}" role="img" aria-label="${escape(label)}" focusable="false" style="display: inline-block; vertical-align: middle; width: ${width / height * (kana ? 3 : 2)}em; height: ${kana ? 3 : 2}em; max-width: 100%;">`
+    + `<title>${escape(label)}</title>${lines.join("")}${dots.join("")}${particle}${labels}</svg>`;
+}
+
+export function ankiPitchGraphs(term, kana = false) {
+  const reading = term.reading || term.expression;
+  return term.pitches.map(group => {
+    const graphs = group.pitches.map(pitch => pitchGraph(reading, pitch, kana)).filter(Boolean);
+    return graphs.length ? `<b>${escape(group.dictionary)}</b>: ${graphs.join(" ")}` : "";
+  }).filter(Boolean).join("<br>");
+}