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/hooks/useSupabase.ts

@@ -2,14 +2,17 @@ import { useCallback } from "react";
 import { useAtom } from "jotai";
 import {
   supabaseProjectsAtom,
+  supabaseBranchesAtom,
   supabaseLoadingAtom,
   supabaseErrorAtom,
   selectedSupabaseProjectAtom,
 } from "@/atoms/supabaseAtoms";
 import { IpcClient } from "@/ipc/ipc_client";
+import { SetSupabaseAppProjectParams } from "@/ipc/ipc_types";
 
 export function useSupabase() {
   const [projects, setProjects] = useAtom(supabaseProjectsAtom);
+  const [branches, setBranches] = useAtom(supabaseBranchesAtom);
   const [loading, setLoading] = useAtom(supabaseLoadingAtom);
   const [error, setError] = useAtom(supabaseErrorAtom);
   const [selectedProject, setSelectedProject] = useAtom(
@@ -35,14 +38,34 @@ export function useSupabase() {
     }
   }, [ipcClient, setProjects, setError, setLoading]);
 
+  /**
+   * Load branches for a Supabase project
+   */
+  const loadBranches = useCallback(
+    async (projectId: string) => {
+      setLoading(true);
+      try {
+        const list = await ipcClient.listSupabaseBranches({ projectId });
+        setBranches(Array.isArray(list) ? list : []);
+        setError(null);
+      } catch (error) {
+        console.error("Error loading Supabase branches:", error);
+        setError(error instanceof Error ? error : new Error(String(error)));
+      } finally {
+        setLoading(false);
+      }
+    },
+    [ipcClient, setBranches, setError, setLoading],
+  );
+
   /**
    * Associate a Supabase project with an app
    */
   const setAppProject = useCallback(
-    async (projectId: string, appId: number) => {
+    async (params: SetSupabaseAppProjectParams) => {
       setLoading(true);
       try {
-        await ipcClient.setSupabaseAppProject(projectId, appId);
+        await ipcClient.setSupabaseAppProject(params);
         setError(null);
       } catch (error) {
         console.error("Error setting Supabase project for app:", error);
@@ -87,10 +110,12 @@ export function useSupabase() {
 
   return {
     projects,
+    branches,
     loading,
     error,
     selectedProject,
     loadProjects,
+    loadBranches,
     setAppProject,
     unsetAppProject,
     selectProject,