Switch language in place, without a reload

Choosing a language in the picker now applies it at once. The choice is
stored and ?lang is kept in step through replaceState, and the picker keeps
focus.

Code that writes translated text itself re-presents it on a switch:
onLocaleChange() lets an owner listen, removed at teardown, and status
writers hand over a function of the locale (voice cards, scene director,
SDR, draw hints, imagery split, map sources, Bhote Koshi media) so the
words are rebuilt rather than re-sent. The HUD, cockpit, radio, CCTV,
launch, awareness and credit texts follow the same hook, and
applyDocumentTranslations can be applied again without undoing text code
wrote since.

The unsaved-work registry and persistLocaleAndReload existed only to guard
the reload, so they go, with their catalog entries.

src/annotations/drawTool.js

@@ -49,7 +49,7 @@ import {
   removeLastVertex,
 } from './drawMode.js';
 
-import { msg, registerUnsavedWork, t, translateKnown } from '../i18n/index.js';
+import { onLocaleChange, t, translateKnown } from '../i18n/index.js';
 /** The id this tool claims the pointer under. */
 const DRAW_POINTER_OWNER = 'draw';
 const PREVIEW_DATA_SOURCE_NAME = 'gev-draw-preview';
@@ -107,17 +107,6 @@ export function initDrawTool({
     target.addEventListener(type, listener, options);
     domListeners.push([target, type, listener, options]);
   };
-  // The board lives only in memory: switching language (a reload) asks first
-  // while it holds a lasting mark or a shape is half drawn.
-  const unregisterUnsavedWork = registerUnsavedWork(() => {
-    if (destroyed) return null;
-    const lasting = (annotations.list?.() || []).some(
-      (mark) => mark && mark.ttlMs == null && !mark.expiring,
-    );
-    return lasting || session?.vertices?.length > 0
-      ? msg('drawings on the map')
-      : null;
-  });
 
   const dataSource = new Cesium.CustomDataSource(PREVIEW_DATA_SOURCE_NAME);
   // `add()` resolves on the NEXT tick, so an init-then-immediate-destroy would
@@ -129,10 +118,17 @@ export function initDrawTool({
   );
 
   const present = () => publish({ active, shape, color, label, hint });
+  // The hint is kept as the call that words it, so a language switch can
+  // word it again.
+  let hintText = () => '';
   const setHint = (text) => {
-    hint = text;
+    hintText = text;
+    hint = text();
     present();
   };
+  const offLocale = onLocaleChange(() => {
+    if (!destroyed) setHint(hintText);
+  });
 
   // ---- preview ---------------------------------------------------------
   const vertexPositions = () =>
@@ -167,7 +163,7 @@ export function initDrawTool({
     previewEntities.length = 0;
     if (!session) {
       previewLine.show = false;
-      setHint(drawHint(null));
+      setHint(() => drawHint(null));
       viewer.scene.requestRender();
       return;
     }
@@ -193,7 +189,7 @@ export function initDrawTool({
         }),
       );
     }
-    setHint(drawHint(session));
+    setHint(() => drawHint(session));
     viewer.scene.requestRender();
   };
 
@@ -216,14 +212,14 @@ export function initDrawTool({
     // A click that changed nothing still deserves an answer when the reason is
     // a limit rather than the harmless tail of a double-click.
     if (reason === 'full')
-      setHint(
+      setHint(() =>
         t(
           'That shape already has {count} points — finish it or press Backspace.',
           { count: MAX_VERTICES },
         ),
       );
     else if (reason === 'invalid')
-      setHint(t('That point is off the globe — click on the world.'));
+      setHint(() => t('That point is off the globe — click on the world.'));
   };
   const onMove = (event) => {
     if (!session || session.shape === 'pin' || destroyed) return;
@@ -241,7 +237,7 @@ export function initDrawTool({
     if (reason !== 'ok') {
       // 'too-few' is just "keep clicking" and the hint already says so;
       // a degenerate or off-globe shape needs to be told why it was refused.
-      if (reason !== 'too-few') setHint(drawHint(session));
+      if (reason !== 'too-few') setHint(() => drawHint(session));
       return null;
     }
     const spec = finishSpec(session, { label, color });
@@ -260,11 +256,12 @@ export function initDrawTool({
         flyTo: false,
       });
       if (destroyed || attempt !== generation) return result;
-      if (result?.drawn === 0) setHint(t('That shape could not be placed.'));
+      if (result?.drawn === 0)
+        setHint(() => t('That shape could not be placed.'));
       return result;
     } catch (error) {
       if (destroyed || attempt !== generation) return null;
-      setHint(
+      setHint(() =>
         t('Could not place the shape: {error}', {
           error: error?.message || error,
         }),
@@ -286,7 +283,7 @@ export function initDrawTool({
     if (session) session = createDrawSession(shape);
     annotations.clear();
     syncPreview();
-    if (!destroyed && !active) setHint(t('Board cleared.'));
+    if (!destroyed && !active) setHint(() => t('Board cleared.'));
   };
 
   // ---- keys: only while drawing, never while typing in another field ----
@@ -354,7 +351,7 @@ export function initDrawTool({
         // Somebody else is using the pointer — possibly an older instance of
         // this same tool that has not finished tearing down. Say so instead of
         // half-starting.
-        setHint(
+        setHint(() =>
           t('{owner} is using the pointer — close it first.', {
             owner: translateKnown(pointerOwnerName(pointerOwner())),
           }),
@@ -459,7 +456,7 @@ export function initDrawTool({
     },
     clearDraw: clearAll,
   });
-  setHint(drawHint(null));
+  setHint(() => drawHint(null));
 
   const api = {
     get active() {
@@ -521,7 +518,7 @@ export function initDrawTool({
       generation += 1;
       if (active) setActive(false);
       destroyed = true;
-      unregisterUnsavedWork();
+      offLocale();
       disconnect();
       releaseSceneHandler();
       releasePointer(lease);