fix(vscode): default to the VS Code display language before a saved locale

The splash and the UI bundle both started in English on a fresh install
even when VS Code ran in a supported language, because only OpenChamber's
own saved locale was consulted. The HTML now exposes VS Code's display
language; the splash and detectInitialLocale use it until the user picks
a locale, which still wins.

Claude-Session: https://claude.ai/code/session_01VqV56Hez25hTxXH4ipJfzH

packages/ui/src/lib/i18n/runtime.ts

@@ -102,11 +102,23 @@ export function writeStoredLocale(locale: Locale): void {
   }
 }
 
+declare global {
+  interface Window {
+    /** The host application's display language (VS Code sets it), used before the user picks a locale. */
+    __OPENCHAMBER_HOST_LANGUAGE__?: string;
+  }
+}
+
 export function detectInitialLocale(): Locale {
   const stored = readStoredLocale();
   if (stored) {
     return stored;
   }
 
+  const hostLanguage = globalThis.window?.__OPENCHAMBER_HOST_LANGUAGE__;
+  if (hostLanguage) {
+    return normalizeLocale(hostLanguage);
+  }
+
   return DEFAULT_LOCALE;
 }

packages/vscode/src/DOCUMENTATION.md

@@ -201,6 +201,10 @@ half-translated locale looks like a shipped feature. `localizationBundles.test.t
 enforces that, and it is the check to run whenever a feature adds a new string.
 
 The pre-bundle loading splash in `webviewHtml.ts` is separate: its strings are
-inlined in the generated HTML and chosen from OpenChamber's own saved locale
+inlined in the generated HTML because the splash renders before the webview
-(`openchamber.i18n.v1` in webview localStorage), not from VS Code's display
+bundle loads. It picks them from OpenChamber's own saved locale
-language, because the splash renders before the webview bundle loads.
+(`openchamber.i18n.v1` in webview localStorage) and, before the user has
+chosen one, from VS Code's display language, which the HTML exposes as
+`window.__OPENCHAMBER_HOST_LANGUAGE__`. The UI bundle reads the same value as
+its default locale (`detectInitialLocale`), so a fresh install in a supported
+language starts in that language on both the splash and the app.

packages/vscode/src/webviewHtml.ts

@@ -195,23 +195,32 @@ export function getWebviewHtml(options: WebviewHtmlOptions): string {
       initialSessionId: ${initialSessionId ? `"${initialSessionId.replace(/\\/g, '\\\\').replace(/"/g, '\\"')}"` : 'null'},
     };
     window.__OPENCHAMBER_HOME__ = "${workspaceFolder.replace(/\\/g, '\\\\')}";
-    
+    // VS Code's display language. The UI bundle uses it as the default locale
-    function getBootstrapMessages() {
+    // until the user picks one; the splash below picks its strings from it too.
-      var locale = 'en';
+    window.__OPENCHAMBER_HOST_LANGUAGE__ = ${JSON.stringify(vscode.env.language)};
+
+    // OpenChamber's own saved locale wins; before one exists, VS Code's display
+    // language decides, so a fresh install in a supported language never boots
+    // in English.
+    function resolveBootstrapLanguage() {
       try {
         var rawLocale = window.localStorage.getItem('openchamber.i18n.v1');
         if (rawLocale) {
           var parsedLocale = JSON.parse(rawLocale);
-          if (parsedLocale && typeof parsedLocale.locale === 'string') {
+          if (parsedLocale && typeof parsedLocale.locale === 'string') return parsedLocale.locale.toLowerCase();
-            var detected = parsedLocale.locale.toLowerCase();
-            if (detected.indexOf('fr') === 0) {
-              locale = 'fr';
-            } else if (detected.indexOf('tr') === 0) {
-              locale = 'tr';
-            }
-          }
         }
       } catch {}
+      return String(window.__OPENCHAMBER_HOST_LANGUAGE__ || '').toLowerCase();
+    }
+
+    function getBootstrapMessages() {
+      var locale = 'en';
+      var detected = resolveBootstrapLanguage();
+      if (detected.indexOf('fr') === 0) {
+        locale = 'fr';
+      } else if (detected.indexOf('tr') === 0) {
+        locale = 'tr';
+      }
 
       if (locale === 'fr') {
         return {
@@ -296,27 +305,19 @@ export function getWebviewHtml(options: WebviewHtmlOptions): string {
 
       const statusEl = document.getElementById('loading-status');
       const getDevMessages = () => {
-        try {
+        const detected = resolveBootstrapLanguage();
-          const rawLocale = window.localStorage.getItem('openchamber.i18n.v1');
+        if (detected.indexOf('fr') === 0) {
-          if (rawLocale) {
+          return {
-            const parsedLocale = JSON.parse(rawLocale);
+            startingDevServer: (host) => 'Démarrage du serveur de développement de la webview (' + host + ')...',
-            if (parsedLocale && typeof parsedLocale.locale === 'string') {
+            waitingDevServer: (host, attempt) => 'En attente du serveur de développement de la webview (' + host + ')... tentative ' + attempt,
-              const detected = parsedLocale.locale.toLowerCase();
+          };
-              if (detected.indexOf('fr') === 0) {
+        }
-                return {
+        if (detected.indexOf('tr') === 0) {
-                  startingDevServer: (host) => 'Démarrage du serveur de développement de la webview (' + host + ')...',
+          return {
-                  waitingDevServer: (host, attempt) => 'En attente du serveur de développement de la webview (' + host + ')... tentative ' + attempt,
+            startingDevServer: (host) => 'Webview dev sunucusu başlatılıyor (' + host + ')...',
-                };
+            waitingDevServer: (host, attempt) => 'Webview dev sunucusu bekleniyor (' + host + ')... deneme ' + attempt,
-              }
+          };
-              if (detected.indexOf('tr') === 0) {
+        }
-                return {
-                  startingDevServer: (host) => 'Webview dev sunucusu başlatılıyor (' + host + ')...',
-                  waitingDevServer: (host, attempt) => 'Webview dev sunucusu bekleniyor (' + host + ')... deneme ' + attempt,
-                };
-              }
-            }
-          }
-        } catch {}
         return {
           startingDevServer: (host) => 'Starting webview dev server (' + host + ')...',
           waitingDevServer: (host, attempt) => 'Waiting for webview dev server (' + host + ')... attempt ' + attempt,