Support Supabase branches (#1394)

<!-- This is an auto-generated description by cubic. -->

## Summary by cubic
Adds Supabase database branch selection per app, with a new schema field
and UI to choose a branch after connecting a project. Resets branch when
changing or disconnecting the project to keep state consistent.

- **New Features**
  - Added apps.supabase_branch_id column.
- Branch dropdown in SupabaseConnector shown after a project is
connected; selection persists and triggers app refresh.
- New state and hooks: supabaseBranchesAtom, loadBranches(projectId),
setAppBranch(branchId).
- IPC endpoints: supabase:list-branches and supabase:set-app-branch;
setting/unsetting project also clears the branch.

- **Migration**
- Apply drizzle migration 0013_supabase_branch.sql to add the
supabase_branch_id column (defaults to null).

<!-- End of auto-generated description by cubic. -->

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Adds Supabase database branch selection per app, including parent
project tracking, new IPC endpoints, UI dropdown, and an accompanying DB
migration with e2e tests.
> 
> - **Database**:
> - Add `apps.supabase_parent_project_id` via migration
`drizzle/0015_complete_old_lace.sql`; snapshot and journal updated.
> - **IPC/Main**:
> - New `supabase:list-branches` handler and management client
`listSupabaseBranches` (real API + test stubs).
> - Update `supabase:set-app-project` to accept `{ projectId,
parentProjectId?, appId }`; unset clears both IDs.
> - `get-app` resolves `supabaseProjectName` using
`supabase_parent_project_id` when present.
> - **Types & Client**:
> - Add `SupabaseBranch`, `SetSupabaseAppProjectParams`, and
`App.supabaseParentProjectId`; expose `listSupabaseBranches` and updated
`setSupabaseAppProject` in `ipc_client` and preload whitelist.
> - **UI/Hooks**:
> - Supabase UI: branch dropdown in `SupabaseConnector` with
`loadBranches`, selection persists via updated `setAppProject`.
> - State: add `supabaseBranchesAtom`; `useSupabase` gets `branches`,
`loadBranches`, new param shape for `setAppProject`.
>   - TokenBar/ChatInput: add `data-testid` for token bar and toggle.
> - **Supabase Context (tests)**:
> - Test build returns large context for `test-branch-project-id` to
validate branch selection.
> - **E2E Tests**:
> - Add `supabase_branch.spec.ts` and snapshot verifying branch
selection affects token usage.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
33054278db8396b4371ed6e8224105cb5684b7ac. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

src/components/SupabaseConnector.tsx

@@ -56,6 +56,8 @@ export function SupabaseConnector({ appId }: { appId: number }) {
     loading,
     error,
     loadProjects,
+    branches,
+    loadBranches,
     setAppProject,
     unsetAppProject,
   } = useSupabase();
@@ -70,7 +72,7 @@ export function SupabaseConnector({ appId }: { appId: number }) {
 
   const handleProjectSelect = async (projectId: string) => {
     try {
-      await setAppProject(projectId, appId);
+      await setAppProject({ projectId, appId });
       toast.success("Project connected to app successfully");
       await refreshApp();
     } catch (error) {
@@ -78,6 +80,14 @@ export function SupabaseConnector({ appId }: { appId: number }) {
     }
   };
 
+  const projectIdForBranches =
+    app?.supabaseParentProjectId || app?.supabaseProjectId;
+  useEffect(() => {
+    if (projectIdForBranches) {
+      loadBranches(projectIdForBranches);
+    }
+  }, [projectIdForBranches, loadBranches]);
+
   const handleUnsetProject = async () => {
     try {
       await unsetAppProject(appId);
@@ -122,9 +132,56 @@ export function SupabaseConnector({ appId }: { appId: number }) {
             </CardDescription>
           </CardHeader>
           <CardContent>
-            <Button variant="destructive" onClick={handleUnsetProject}>
-              Disconnect Project
-            </Button>
+            <div className="space-y-4">
+              <div className="space-y-2">
+                <Label htmlFor="supabase-branch-select">Database Branch</Label>
+                <Select
+                  value={app.supabaseProjectId || ""}
+                  onValueChange={async (supabaseBranchProjectId) => {
+                    try {
+                      const branch = branches.find(
+                        (b) => b.projectRef === supabaseBranchProjectId,
+                      );
+                      if (!branch) {
+                        throw new Error("Branch not found");
+                      }
+                      await setAppProject({
+                        projectId: branch.projectRef,
+                        parentProjectId: branch.parentProjectRef,
+                        appId,
+                      });
+                      toast.success("Branch selected");
+                      await refreshApp();
+                    } catch (error) {
+                      toast.error("Failed to set branch: " + error);
+                    }
+                  }}
+                  disabled={loading}
+                >
+                  <SelectTrigger
+                    id="supabase-branch-select"
+                    data-testid="supabase-branch-select"
+                  >
+                    <SelectValue placeholder="Select a branch" />
+                  </SelectTrigger>
+                  <SelectContent>
+                    {branches.map((branch) => (
+                      <SelectItem
+                        key={branch.projectRef}
+                        value={branch.projectRef}
+                      >
+                        {branch.name}
+                        {branch.isDefault && " (Default)"}
+                      </SelectItem>
+                    ))}
+                  </SelectContent>
+                </Select>
+              </div>
+
+              <Button variant="destructive" onClick={handleUnsetProject}>
+                Disconnect Project
+              </Button>
+            </div>
           </CardContent>
         </Card>
       );

src/components/chat/ChatInput.tsx

@@ -351,6 +351,7 @@ export function ChatInput({ chatId }: { chatId?: number }) {
                       showTokenBar ? "text-purple-500 bg-purple-100" : ""
                     }`}
                     size="sm"
+                    data-testid="token-bar-toggle"
                   >
                     <ChartColumnIncreasing size={14} />
                   </Button>

src/components/chat/TokenBar.tsx

@@ -67,7 +67,7 @@ export function TokenBar({ chatId }: TokenBarProps) {
   const inputPercent = (inputTokens / contextWindow) * 100;
 
   return (
-    <div className="px-4 pb-2 text-xs">
+    <div className="px-4 pb-2 text-xs" data-testid="token-bar">
       <TooltipProvider>
         <Tooltip>
           <TooltipTrigger asChild>