feat(git-sync): per-space 'Enable Git sync' toggle (Phase C, §7.1)

UI opt-in for git-sync, mirroring the existing sharing/comments settings pattern
(no new endpoint, no new mechanism; orchestrator read query untouched):
- UpdateSpaceDto.gitSyncEnabled?: boolean.
- SpaceRepo.updateGitSyncSettings: jsonb-merge into settings.gitSync.<key>
  (COALESCE || jsonb_build_object — never clobbers sibling sharing/comments);
  stored as a real jsonb boolean so the orchestrator's
  settings->'gitSync'->>'enabled' = 'true' matches.
- SpaceService.updateSpace handles the flag (audit diff) via the existing
  CASL-guarded space update path (Manage/Settings).
- client: Switch in edit-space-form (optimistic mutate + revert-on-error,
  readOnly-aware) + space types + 2 i18n keys.
- space.service.spec extended (calls updateGitSyncSettings; no-op when undefined).
tsc clean (server+client); jest src/core/space 4 pass.

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

apps/client/src/features/space/components/edit-space-form.tsx

@@ -1,5 +1,14 @@
-import { Group, Box, Button, TextInput, Stack, Textarea } from "@mantine/core";
-import React from "react";
+import {
+  Group,
+  Box,
+  Button,
+  TextInput,
+  Stack,
+  Textarea,
+  Divider,
+  Switch,
+} from "@mantine/core";
+import React, { useState } from "react";
 import { useForm } from "@mantine/form";
 import { zod4Resolver } from "mantine-form-zod-resolver";
 import { z } from "zod/v4";
@@ -29,6 +38,23 @@ export function EditSpaceForm({ space, readOnly }: EditSpaceFormProps) {
   const { t } = useTranslation();
   const updateSpaceMutation = useUpdateSpaceMutation();
 
+  const [gitSyncEnabled, setGitSyncEnabled] = useState<boolean>(
+    space?.settings?.gitSync?.enabled ?? false,
+  );
+
+  const handleGitSyncToggle = async (value: boolean) => {
+    const previous = gitSyncEnabled;
+    setGitSyncEnabled(value); // optimistic update
+    try {
+      await updateSpaceMutation.mutateAsync({
+        spaceId: space.id,
+        gitSyncEnabled: value,
+      });
+    } catch (err) {
+      setGitSyncEnabled(previous); // revert on failure
+    }
+  };
+
   const form = useForm<FormValues>({
     validate: zod4Resolver(formSchema),
     initialValues: {
@@ -104,6 +130,18 @@ export function EditSpaceForm({ space, readOnly }: EditSpaceFormProps) {
             </Group>
           )}
         </form>
+
+        <Divider my="lg" />
+
+        <Switch
+          label={t("Enable Git sync")}
+          description={t("Sync this space's pages to a Git repository.")}
+          checked={gitSyncEnabled}
+          disabled={readOnly || updateSpaceMutation.isPending}
+          onChange={(event) =>
+            handleGitSyncToggle(event.currentTarget.checked)
+          }
+        />
       </Box>
     </>
   );

apps/client/src/features/space/types/space.types.ts

@@ -13,9 +13,14 @@ export interface ISpaceCommentsSettings {
   allowViewerComments?: boolean;
 }
 
+export interface ISpaceGitSyncSettings {
+  enabled?: boolean;
+}
+
 export interface ISpaceSettings {
   sharing?: ISpaceSharingSettings;
   comments?: ISpaceCommentsSettings;
+  gitSync?: ISpaceGitSyncSettings;
 }
 
 export interface ISpace {
@@ -35,6 +40,7 @@ export interface ISpace {
   // for updates
   disablePublicSharing?: boolean;
   allowViewerComments?: boolean;
+  gitSyncEnabled?: boolean;
 }
 
 interface IMembership {