fix(startup): async dictionary loading and unblock first tokenization

- move JLPT/frequency dictionary init off sync fs APIs and add cooperative yielding during entry processing

- decouple first tokenization from full warmup by gating only on Yomitan readiness while MeCab/dictionary warmups continue in parallel

- update mpv pause-until-ready OSD copy to tokenization-focused wording and refresh gate regression assertions

src/core/services/jlpt-vocab.test.ts

@@ -0,0 +1,72 @@
+import assert from 'node:assert/strict';
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+import test from 'node:test';
+
+import { createJlptVocabularyLookup } from './jlpt-vocab';
+
+test('createJlptVocabularyLookup loads JLPT bank entries and resolves known levels', async () => {
+  const logs: string[] = [];
+  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'subminer-jlpt-dict-'));
+  fs.writeFileSync(
+    path.join(tempDir, 'term_meta_bank_5.json'),
+    JSON.stringify([
+      ['猫', 1, { frequency: { displayValue: 1 } }],
+      ['犬', 2, { frequency: { displayValue: 2 } }],
+    ]),
+  );
+  fs.writeFileSync(path.join(tempDir, 'term_meta_bank_1.json'), JSON.stringify([]));
+  fs.writeFileSync(path.join(tempDir, 'term_meta_bank_2.json'), JSON.stringify([]));
+  fs.writeFileSync(path.join(tempDir, 'term_meta_bank_3.json'), JSON.stringify([]));
+  fs.writeFileSync(path.join(tempDir, 'term_meta_bank_4.json'), JSON.stringify([]));
+
+  const lookup = await createJlptVocabularyLookup({
+    searchPaths: [tempDir],
+    log: (message) => {
+      logs.push(message);
+    },
+  });
+
+  assert.equal(lookup('猫'), 'N5');
+  assert.equal(lookup('犬'), 'N5');
+  assert.equal(lookup('鳥'), null);
+  assert.equal(logs.some((entry) => entry.includes('JLPT dictionary loaded from')), true);
+});
+
+test('createJlptVocabularyLookup does not require synchronous fs APIs', async () => {
+  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), 'subminer-jlpt-dict-'));
+  fs.writeFileSync(
+    path.join(tempDir, 'term_meta_bank_4.json'),
+    JSON.stringify([['見る', 1, { frequency: { displayValue: 3 } }]]),
+  );
+  fs.writeFileSync(path.join(tempDir, 'term_meta_bank_1.json'), JSON.stringify([]));
+  fs.writeFileSync(path.join(tempDir, 'term_meta_bank_2.json'), JSON.stringify([]));
+  fs.writeFileSync(path.join(tempDir, 'term_meta_bank_3.json'), JSON.stringify([]));
+  fs.writeFileSync(path.join(tempDir, 'term_meta_bank_5.json'), JSON.stringify([]));
+
+  const readFileSync = fs.readFileSync;
+  const statSync = fs.statSync;
+  const existsSync = fs.existsSync;
+  (fs as unknown as Record<string, unknown>).readFileSync = () => {
+    throw new Error('sync read disabled');
+  };
+  (fs as unknown as Record<string, unknown>).statSync = () => {
+    throw new Error('sync stat disabled');
+  };
+  (fs as unknown as Record<string, unknown>).existsSync = () => {
+    throw new Error('sync exists disabled');
+  };
+
+  try {
+    const lookup = await createJlptVocabularyLookup({
+      searchPaths: [tempDir],
+      log: () => undefined,
+    });
+    assert.equal(lookup('見る'), 'N4');
+  } finally {
+    (fs as unknown as Record<string, unknown>).readFileSync = readFileSync;
+    (fs as unknown as Record<string, unknown>).statSync = statSync;
+    (fs as unknown as Record<string, unknown>).existsSync = existsSync;
+  }
+});