refactor(i18n): key messages by English text; add Russian

Replace the semantic keys with the English source text, so code reads as the
UI does and English needs no catalog: t('Save keys'), tn(count, one, other)
for plurals, msg() for text stored in data, and bare data-i18n* markup that
translates the element's own English. Other languages are one flat JSON each.

- Simplify src/i18n: drop namespaces, the configurable locale pair
  (GEV_DEFAULT_LOCALE / GEV_SECONDARY_LOCALE) and its build defines. Locale
  comes from ?lang=, the stored choice, then browser languages.
- Add scripts/i18n.mjs (npm run i18n): extracts every message from t/tn/msg
  and markup, and fails on missing, unused, placeholder-mismatched or
  wrongly-shaped plural entries. npm test runs it via catalog.test.mjs.
- Add Russian (src/i18n/locales/ru.json, 833 messages), started from the
  community catalog in #312 and reviewed against the current English.
- Fix data-i18n placed on parents that would wipe their children (cockpit
  LEVEL and local weather cells, first-run EXPLORE MANUALLY tile), and a
  doubled degree sign in the TRACK ACQUIRED signal.
- Rewrite docs/TRANSLATORS.md for the new workflow; drop sections the earlier
  merge resurrected in docs/CURRENT-STATE.md.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/CURRENT-STATE.md

@@ -3009,124 +3009,28 @@ test:track` 43 tracking invariants · headless QA harnesses under
 > attribution 18/18). New modules: `src/data/{motionModel,aircraftMeta,aircraftClass,aircraftIcons,issPass,routePlausible,dataCredits}.js`.
 > The live runtime now declares 30 voice tools; the 17→20 count above is retained only as milestone history.
 
-### Internationalization / catalog locales (September 2026)
+### Interface localization (October 2026)
 
-The application-owned UI is fully extracted into message catalogs; **en**
-is the only shipped locale in this foundation state — additional locales
-land as stacked follow-up PRs, one per locale (Spanish first), each
-following the locale-addition recipe in
-[`docs/TRANSLATORS.md`](./TRANSLATORS.md). English is the default, the
-source catalog, and the fallback. The subsystem lives in `src/i18n/`:
+Shipped locales: **en** (source and fallback) and **ru**. The code lives in
+`src/i18n/`; the contributor workflow is in [`docs/TRANSLATORS.md`](./TRANSLATORS.md).
 
-- **File map.** `src/i18n/locale.js` owns locale resolution, guarded storage
-  (`gev:locale:v1`), the one-shot `?lang=` override, and `<html lang>`/`<html
-  dir>` metadata. `src/i18n/index.js` owns the catalog registry, `t()`
-  (interpolation + `Intl.PluralRules` plural selection), `formatNumber` /
-  `formatDate`, `applyDocumentTranslations()`, and
-  `persistLocaleAndReload()`. The shipped catalog is four flat message maps
-  — `src/i18n/locales/en/{shell,cockpit,layers,setup}.js`, 912 keys (shell
-  34, cockpit 369, layers 388, setup 121). Plural entries are the en
-  `{ one, other }` shape; a future locale may add only cardinal categories
-  `Intl.PluralRules` reports valid for it, and an entry lacking the selected
-  category degrades to `other` at runtime. Locale-code normalization
-  (`es-MX`/`es_419` → `es`, plus fr/ru/uk and variants) ships ahead of the
-  locales on purpose: knowing a code is hygiene, shipping is catalog-driven
-  through `CATALOG_LOCALES`.
-- **Selector.** The command dock carries a compact locale switch: a static
-  `.dock-locale-switch` group container in `index.html` whose buttons
-  (`.dock-locale-btn`) are rendered at runtime by `src/ui/applicationShell.js`
-  `_initLocaleSelector()` — one per locale in the configured pair; while
-  only English ships that is a single EN button. A click persists the
-  choice and reloads the page with the hash preserved, so no live re-apply
-  of already-rendered dynamic panels is needed.
-- **Locale pair config.** `GEV_DEFAULT_LOCALE` and `GEV_SECONDARY_LOCALE` in
-  `.env`, injected as `import.meta.env` defines by `vite.config.js`; both
-  values are validated against the shipped catalogs (`CATALOG_LOCALES`),
-  and the offered set is `dedup([default, secondary, 'en'])`. While English
-  is the only shipped catalog the built-in pair is en-only, so every
-  configuration degenerates to a single offered locale; an invalid,
-  unshipped, or degenerate configured pair falls back to that built-in
-  en-only shape (dev-only warn). The first secondary-locale PR restores the
-  built-in en+es pair.
-- **Resolution order.** `?lang=<locale>` (search string only; never
-  persisted, never written into share links; stripped by
-  `persistLocaleAndReload`; accepted only for offered locales) → stored
-  `gev:locale:v1` (re-checked against the pair) →
-  `navigator.languages` (regional variants normalize to the primary tag:
-  `es-MX`/`es_419` → `es`) → the CONFIGURED default locale. Unsupported
-  values defer to the next
-  step rather than forcing English.
-- **Gates** (all under `node --test src/i18n/`, 40 tests):
-  `catalog.test.mjs` enforces per-locale key, placeholder-name, and
-  plural-shape parity with the strict exact-parity flip ON
-  (`REQUIRE_FULL_PARITY`; `GEV_I18N_REQUIRE_FULL_LOCALE_PARITY=0` opts out
-  for staged work; the loops are vacuous while only en ships — each locale
-  PR meets them from day one);
-  `markupCoverage.test.mjs` requires every `data-i18n*` attribute in
-  `index.html` to resolve in every shipped catalog and rejects unknown attribute
-  spellings; `i18n.test.mjs` pins precedence, guards, fallback,
-  interpolation, the plural-selection contract (synthetic missing-category
-  degradation; real-catalog plural pins arrive with each locale PR), and
-  DOM application; `repairPass.test.mjs` anchors en byte-identity for
-  extracted literals and rejects a locale-scoped CCTV wrap rule shipping
-  ahead of its locale (per-locale value anchors arrive with each locale
-  PR).
-- **Accepted deferrals (do not "fix" silently):**
-  - The military-awareness subject header literal `FLIGHT / VESSEL WINDOW`
-    (`src/data/militaryAwareness.js`) stays English; the literal is
-    test-pinned in `src/data/militaryAwareness.test.mjs`.
-  - The visible cockpit-brief tab tokens `SIG` / `NEWS` / `LOCAL`
-    (`index.html`) stay untranslated to match the runtime keys; their
-    `aria-label`s ARE localized (`cockpit.brief.tab*AriaLabel`).
-  - `src/voice/gevActions.js` tool-result confirmation strings stay English
-    by contract (voice tool schemas and spoken confirmations are
-    keep-English; see the Keep-English boundary in `docs/TRANSLATORS.md`).
-  - Number formatting is still the pre-i18n `toLocaleString` policy at:
-    `src/ui.js:1442`, `src/data/satellites.js:829`,
-    `src/data/flights.js:436` (`'en-US'` pinned), and
-    `src/data/rocketLaunches.js:2281/2299/2364/2371/2374`
-    (default-locale). A locale-aware number-format policy is deferred; the
-    `formatNumber` helper exists in `src/i18n/index.js` when that lands.
-
-### Overpass proxy mirror rotation (September 2026)
-
-- `/api/overpass` fans out across four public mirrors. `overpassPayloadIsData()` governs cache reads, writes, and stale fallback: only a 2xx that is neither rate-limited nor a body-level runtime error qualifies. Previously stored refusals are ignored on both fresh and stale reads, so upgrading does not require manually clearing the disk cache.
-- HTTP refusals such as 406 now rotate alongside the existing network, rate-limit, and runtime-error cases. A refusal from one mirror no longer prevents reaching healthy alternatives or persists under the seven-day road/month-long boundary cache TTLs. Concurrent identical queries share one mirror sequence; if it fails, both the initiating and joined callers can use the same last-good data.
-- A refusal every mirror agrees on is still reported with the first mirror's status and body, so a genuinely malformed query says what upstream said — but only after every mirror has had the chance to answer it. `fetchOverpassPayload` takes injectable endpoints and fetch so the rotation is tested without a live mirror (`src/overpassProxy.test.mjs`).
-
-### Share-link v2 layer state (August 2026)
-
-- Generated share links use a deterministic v2 hash. Existing camera, visual,
-  HUD, detection, post-processing, celestial, scope, and map-stack fields remain,
-  with compact fields for enabled layers, allowlisted layer options, panel state,
-  and the active preset's allowlisted shader controls. An absent layer field uses
-  deterministic defaults; an explicit empty field means no enabled layers.
-- The registry seals only after all 16 production layers register, and every
-  layer has an explicit serialization disposition. Unknown enabled-layer tokens
-  reject the layer payload; unknown option tokens are ignored. Restoration
-  settles independently per layer so one failed or unavailable source cannot
-  block its siblings.
-- Stable visible options are limited to aircraft 3D mode, selected civilian and
-  military flight IDs, Satellite catalog and selection, CCTV coverage/projection/
-  auto-hop, and Radio filter/volume. Playback and tuning, live-data health,
-  calibration, caches, lifecycle state, temporary Context ownership, and derived
-  effects are deliberately excluded. Radio restore never selects or plays a
-  station.
-- Normal loads restore the last successful explicit UI, voice, or tool choice
-  from versioned local storage. Any valid camera share wins for the current load
-  without overwriting recipient preferences. Restore ownership is split by
-  visibility, option/selection, camera, visual, map, and individual panel lane:
-  a newer explicit action supersedes only the field it owns. In particular,
-  navigation cannot turn unrelated layers off, and an option change cannot
-
-#### Keep-English adjudications (post-merge catch-ups)
-
-- `src/ui/visualPresets.js` `'ELASTIC'` — detection-allocation STRATEGY IDENTIFIER (persisted
-  under `gev:detection-allocation`, compared via `dataset.allocation ===`), not display copy.
-- `src/ui/layerPanel.js` guidance meta — the `{source} · {statusMessage}` composition uses a
-  locale-neutral interpunct; the statusMessage itself IS localized via `installationFeedback`.
-- `src/ui/mapSourceControls.js` `'...'` switching label and the orbit `'↻'` glyph —
-  punctuation/glyphs, identical across locales.
+- **Keys are the English text.** `t('Save keys')`, `tn(count, '{count} camera',
+  '{count} cameras')`, and `msg('Live Flights')` for text stored in data and
+  translated later. Markup opts in with `data-i18n` (element text) and
+  `data-i18n-title` / `-aria-label` / `-placeholder` (that attribute's English
+  value). English has no catalog; every other locale is
+  `src/i18n/locales/<code>.json`, and a missing entry falls back to English.
+- **Locale choice.** `?lang=` (one-shot) → stored choice (`gev:locale:v1`) →
+  `navigator.languages` → English. The EN/RU switch in the Visual Presets dock
+  stores the choice and reloads, so nothing re-renders live.
+- **Gate.** `npm run i18n` (and `src/i18n/catalog.test.mjs` under `npm test`)
+  extracts every message and fails on missing, unused, placeholder-mismatched or
+  wrongly-shaped plural entries.
+- **Not translated by design:** layer ids, share-link and hash parameters, API
+  fields, voice tool schemas, provider names, feed data (callsigns, vessel and
+  station names) and attribution.
+- **Gaps.** Strings added after #601's extraction (for example the Street Level
+  panel) are still raw English; there is no lint for unmarked UI text yet.
 
 ## Canonical Docs Order