fix(hud): keep English out of localized summaries, cap ja/zh by characters only

Second follow-up review fixes:

- Japanese and Chinese summaries are capped at 20 characters only, without
  the five-token cut first, and the cap steps back to a space instead of
  splitting a Latin word.
- The HUD request sends localized layer names in feedProvenance too and
  leaves the English narration note out outside English. A non-English reply
  that still echoes a feed-state id or a translated English layer name falls
  back to the deterministic line.
- A camera move during typing shows the deterministic line, not a fragment.
- A view with no place labels and no enabled layer does not ask the model.
- Behaviour tests on IntelHUD replace the regex checks of hud.js; docs and
  the instruction wording updated.

src/hudSummaryLine.test.mjs

@@ -0,0 +1,145 @@
+// The HUD summary line in another language: what the model is sent and what
+// the readout shows. hud.js imports `mgrs`, which Node's ESM loader cannot
+// read named exports from, so a module hook swaps it for a stub before the
+// import (the same setup as hudSummaryGate.test.mjs).
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { registerHooks } from 'node:module';
+
+const MGRS_STUB_URL = 'gev-test-stub:mgrs';
+registerHooks({
+  resolve(specifier, context, next) {
+    if (specifier === 'mgrs') return { url: MGRS_STUB_URL, shortCircuit: true };
+    return next(specifier, context);
+  },
+  load(url, context, next) {
+    if (url === MGRS_STUB_URL) {
+      return {
+        format: 'module',
+        shortCircuit: true,
+        source:
+          'export function forward() { return "10SEG55776339"; }\nexport default { forward };\n',
+      };
+    }
+    return next(url, context);
+  },
+});
+
+const { IntelHUD } = await import('./hud.js');
+const { setLocale } = await import('./i18n/index.js');
+const { hudSummaryInput } = await import('./hudSummaryResponse.js');
+
+const PARTIAL_FLIGHTS = {
+  id: 'flights',
+  name: 'Live Flights',
+  enabled: true,
+  stats: { count: 4, partial: true, source: 'opensky' },
+};
+
+/** A ru HUD over one partial Live Flights layer, answering with `reply`. */
+function createHud(t, reply) {
+  const summary = { textContent: '' };
+  const previous = { document: globalThis.document, window: globalThis.window };
+  globalThis.document = {
+    hidden: false,
+    visibilityState: 'visible',
+    getElementById: (id) => (id === 'hud-summary' ? summary : null),
+    querySelectorAll: () => [],
+    addEventListener() {},
+    removeEventListener() {},
+  };
+  globalThis.window ??= {
+    setTimeout,
+    clearTimeout,
+    setInterval,
+    clearInterval,
+  };
+  t.mock.timers.enable({ apis: ['setInterval'] });
+  const viewer = {
+    scene: { canvas: { width: 0, height: 0 }, pickPositionSupported: false },
+    camera: {
+      pitch: -Math.PI / 2,
+      heading: 0,
+      positionCartographic: { latitude: 0.53, longitude: -1.7, height: 600 },
+      computeViewRectangle: () => undefined,
+      moveStart: { addEventListener() {}, removeEventListener() {} },
+      moveEnd: { addEventListener() {}, removeEventListener() {} },
+    },
+  };
+  const sent = [];
+  const hud = new IntelHUD(viewer, {
+    summaryService: {
+      configured: async () => true,
+      async summarize(context) {
+        sent.push(context);
+        return { ok: true, status: 200, data: { error: null, ...reply } };
+      },
+    },
+  });
+  t.after(() => {
+    hud.destroy();
+    setLocale('en');
+    for (const [key, value] of Object.entries(previous)) {
+      if (value === undefined) delete globalThis[key];
+      else globalThis[key] = value;
+    }
+  });
+  hud._dataManager = { getAll: () => [PARTIAL_FLIGHTS] };
+  hud._latestMetrics = { altM: 600 };
+  setLocale('ru');
+  return { hud, sent, shown: () => summary.textContent };
+}
+
+test('a ru HUD request carries no English layer name', async (t) => {
+  const { hud } = createHud(t, {});
+  const context = await hud._summaryContext();
+  assert.equal(context.locale, 'ru');
+  assert.deepEqual(context.enabledLayerLabels, ['Рейсы онлайн']);
+  const input = hudSummaryInput(context);
+  assert.doesNotMatch(input, /Live Flights/, input);
+  // The locale signs the dedupe signature; the English names stay local.
+  assert.match(JSON.stringify(context), /"locale":"ru"/);
+  assert.doesNotMatch(JSON.stringify(context), /translatedLayerNames/);
+});
+
+test('a ru summary shows the state word first and the layer names last', async (t) => {
+  const { hud, shown } = createHud(t, {
+    summary: 'Аэропорт задерживает рейсы',
+    feedState: 'partial',
+  });
+  await hud._updateSummary(false, true);
+  assert.equal(shown(), 'ЧАСТИЧНО | Аэропорт задерживает рейсы | РЕЙСЫ ОНЛАЙН');
+});
+
+for (const words of [
+  'Live Flights частично онлайн',
+  'Рейсы онлайн stale данные',
+]) {
+  test(`a ru reply echoing English falls back: ${words}`, async (t) => {
+    const { hud, shown } = createHud(t, {
+      summary: words,
+      feedState: 'partial',
+    });
+    await hud._updateSummary(false, true);
+    assert.ok(shown().startsWith('ЧАСТИЧНО | '), shown());
+    assert.ok(!shown().includes(words), shown());
+  });
+}
+
+test('a camera move during typing shows the plain line, not a fragment', (t) => {
+  const { hud, shown } = createHud(t, {});
+  hud._setSummaryText('ЧАСТИЧНО | Аэропорт задерживает рейсы', true);
+  hud._onCameraMoveStart();
+  assert.equal(shown(), hud._composeSummary());
+});
+
+test('a view with no labels and no layers does not ask the model', async (t) => {
+  const { hud, sent, shown } = createHud(t, {
+    summary: 'пусто',
+    feedState: null,
+  });
+  hud._dataManager = { getAll: () => [] };
+  await hud._updateSummary(false, true);
+  assert.equal(sent.length, 0);
+  assert.equal(shown(), hud._composeSummary());
+});