refactor(ai): drop Generative AI flag, gate title generation on AI chat

Remove the separate, un-toggleable `settings.ai.generative` workspace flag
(and its write-side alias `generativeAi`) along with the dead "Ask AI"
generative editor menu, and re-gate the AI page-title generation on the
general AI chat flag (`settings.ai.chat`) — the same toggle that enables
the chat agent and the chat stream endpoint.

Why: the `generative` flag had no UI toggle (its switch was already removed,
leaving orphaned i18n strings), so the title-generation button was
unreachable on self-hosted. The "Ask AI" menu was dead — its atom was never
rendered. Consolidating onto the AI chat flag makes the title button follow
the one AI switch users actually have.

Changes:
- server: title-gen endpoint gate generative -> chat (ai-chat.controller.ts);
  remove generativeAi from update DTO and workspace service (update block,
  delete line, cloud default now { ai: { chat: true } }); fix repo comment;
  migrate generate-page-title spec assertions generative -> chat.
- client: title-gen gate -> settings.ai.chat (full-editor.tsx); remove the
  dead Ask AI button + showAiMenu wiring from bubble-menu; remove AskAiGroup
  usage/import and commented block from fixed-toolbar; delete ask-ai-group.tsx;
  remove showAiMenuAtom; drop generative/generativeAi from workspace types.
- i18n: remove 3 orphaned generative-AI keys from all 12 locales.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/server/src/core/workspace/dto/update-workspace.dto.ts

@@ -31,10 +31,6 @@ export class UpdateWorkspaceDto extends PartialType(CreateWorkspaceDto) {
   @IsBoolean()
   aiSearch: boolean;
 
-  @IsOptional()
-  @IsBoolean()
-  generativeAi: boolean;
-
   @IsOptional()
   @IsBoolean()
   disablePublicSharing: boolean;

apps/server/src/core/workspace/services/workspace.service.ts

@@ -145,7 +145,7 @@ export class WorkspaceService {
           status = WorkspaceStatus.Active;
           plan = 'standard';
           billingEmail = user.email;
-          settings = { ai: { generative: true, chat: true } };
+          settings = { ai: { chat: true } };
         }
 
         // create workspace
@@ -439,20 +439,6 @@ export class WorkspaceService {
         );
       }
 
-      if (typeof updateWorkspaceDto.generativeAi !== 'undefined') {
-        const prev = settingsBefore?.ai?.generative ?? false;
-        if (prev !== updateWorkspaceDto.generativeAi) {
-          before.generativeAi = prev;
-          after.generativeAi = updateWorkspaceDto.generativeAi;
-        }
-        await this.workspaceRepo.updateAiSettings(
-          workspaceId,
-          'generative',
-          updateWorkspaceDto.generativeAi,
-          trx,
-        );
-      }
-
       if (typeof updateWorkspaceDto.disablePublicSharing !== 'undefined') {
         const prev = settingsBefore?.sharing?.disabled ?? false;
         if (prev !== updateWorkspaceDto.disablePublicSharing) {
@@ -587,7 +573,6 @@ export class WorkspaceService {
 
       delete updateWorkspaceDto.restrictApiToAdmins;
       delete updateWorkspaceDto.aiSearch;
-      delete updateWorkspaceDto.generativeAi;
       delete updateWorkspaceDto.disablePublicSharing;
       delete updateWorkspaceDto.mcpEnabled;
       delete updateWorkspaceDto.allowMemberTemplates;