docs(i18n): translator's guide for the en-only foundation, current-state and changelog

docs/TRANSLATORS.md is rewritten for the foundation state: English
shipped, and the locale-addition recipe front and center — the
one-PR-per-locale procedure (catalogs, registration, CATALOG_LOCALES,
pair behavior, parity gates). CURRENT-STATE.md documents the subsystem
(file map, resolution order, selector, gates, deferrals) and the
CHANGELOG records the foundation.

CHANGELOG.md

@@ -76,6 +76,29 @@
   keeps frame time with ALPR on within a few percent of ALPR off, seats nearby
   badges on the rendered surface and says when no loaded camera is on screen.
 
+## Internationalization foundation
+
+- Add the locale core (`src/i18n/`): configurable locale pair
+  (`GEV_DEFAULT_LOCALE` / `GEV_SECONDARY_LOCALE`, validated against the
+  shipped catalogs), guarded preference storage, a one-shot `?lang=`
+  override, and `<html lang>`/`<html dir>` metadata. English is the only
+  shipped locale — the built-in pair degenerates to en-only and the dock
+  language switch renders a single EN button — and English behavior is
+  byte-identical to before.
+- Extract all application-owned presentation text into four English
+  catalogs (`shell`/`cockpit`/`layers`/`setup`) consumed through `t()` call
+  sites, `data-i18n*` template attributes, and the runtime locale selector;
+  complete the duplicate `data-i18n` split on the first-run EXPLORE
+  MANUALLY tile (the subcopy was wiped in every locale).
+- Enforce the parity gates every additional locale must pass (key /
+  placeholder / plural-shape parity, markup coverage, repair-pass anchors).
+  Additional locales ship as stacked follow-up PRs, one per locale, via the
+  locale-addition recipe in `docs/TRANSLATORS.md` (Spanish is first).
+
+- Let CLI tools, development launchers and the setup doctor use an explicit project directory while retaining their existing default paths.
+
+- Split application scene, controls, catalog, tools and HTML into reusable components; configure application request services and sources without changing global fetch. Preserve standalone markup and voice behavior. Explicit annotation navigation may resolve a distant named target.
+
 - CCTV cameras whose bearing is a guess now say so. Packs mark bearings derived
   from a hash of the camera id as `headingConfidence: 'low'`, but nothing read the
   flag, so roughly 70% of a default catalog rendered like surveyed facings. The HUD
@@ -497,11 +520,6 @@ Analyst records for loaded satellites, datacenters and dams, with explicit bound
 - Separate navigation, share restoration, visual settings and panel state into focused UI owners with explicit dependencies and terminal cleanup.
 
 - Separate layer lifecycle transactions from panel construction and render/detection reactions; retain existing transition and refresh behavior.
-
-- Let CLI tools, development launchers and the setup doctor use an explicit project directory while retaining their existing default paths.
-
-- Split application scene, controls, catalog, tools and HTML into reusable components; configure application request services and sources without changing global fetch. Preserve standalone markup and voice behavior. Explicit annotation navigation may resolve a distant named target.
-
 ## Satellite pass prediction
 
 - Bisect pass rise/set to ~0.2 s and fit peak elevation with a parabola.