fix custom provider credentials, edit path, and failure UX

Require an API key or {env:VAR} on client and server, add edit/prefill for
existing custom providers, save auth before config, and surface incomplete
auth plus disconnect after partial failures. Add VS Code parity tests and
drop the unused allProvidersConnected locale key.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/web/server/lib/opencode/routes.js

@@ -482,14 +482,16 @@ export const registerOpenCodeRoutes = (app, dependencies) => {
         }
       }
 
-      const result = upsertProviderConfig(providerID, config, directory, scope);
+      const { getProviderAuth } = await getAuthLibrary();
+      const hasStoredAuth = Boolean(getProviderAuth(providerID));
+      const upsertResult = upsertProviderConfig(providerID, config, directory, scope, { hasStoredAuth });
       await refreshOpenCodeAfterConfigChange(`provider ${providerID} upserted (${scope})`);
 
       return res.json({
         success: true,
-        providerId: result.providerId,
-        path: result.path,
-        config: result.config,
+        providerId: upsertResult.providerId,
+        path: upsertResult.path,
+        config: upsertResult.config,
         requiresReload: true,
         reloadDelayMs: clientReloadDelayMs,
       });