Context

The "Load All" button rendered in the source chunk browser is currently
hard-coded English:

// packages/memtomem/src/memtomem/web/static/app.js:3091
loadAllBtn.textContent = 'Load All';

The KO locale shows Load All in English alongside otherwise-localized
UI. Discovered while reviewing PR #678 (Timeline → Source jump
follow-ups) — the new toast.chunk_target_missing originally said "try
Load All" in both locales, which was a tell that the button itself
wasn't going through t().

Same i18n surface as PR #29 (chunks.* / common.* / toast.* keys) and
PR #587 (langchange follow-through).

What we want

Promote 'Load All' to a locale key — e.g. chunks.load_all —
following the existing patterns:

const loadAllLabel = (typeof t === 'function')
  ? t('chunks.load_all') : 'Load All';
loadAllBtn.textContent = loadAllLabel;
loadAllBtn.setAttribute('data-i18n', 'chunks.load_all');

data-i18n is required for the langchange hook (feedback_data_i18n_ nested_children.md, i18n.js applyDOM()) to keep the label in sync
when the user toggles KO/EN at runtime.

Files

• packages/memtomem/src/memtomem/web/static/app.js (line 3091)
• packages/memtomem/src/memtomem/web/static/locales/en.json
  — add chunks.load_all: "Load All"
• packages/memtomem/src/memtomem/web/static/locales/ko.json
  — add chunks.load_all: "전체 불러오기" (or similar)

Acceptance criteria

• app.js?v= cache-bust bumped (per feedback_static_asset_cache_ bust.md).
• test_i18n.py parity passes (en + ko have the new key).
• KO locale shows the translated label on first paint and after a
  langchange toggle.
• No regression on Source tab chunk browser (button still wires to
  browseSource(path, 500)).

Difficulty

Good first issue: ≤ 3 files (app.js + 2 locales), no API break,
piggyback-eligible if any other small i18n cleanup ships in the same
window.