feat: add prepush lifecycle hook (#498)

* feat: add prepush lifecycle hook

Add `prepushScript` configuration — an optional shell script that runs
automatically before pushing code to the remote repository. Reuses the
existing `executeLifecycleHook` infrastructure (bash execution, 2-min
timeout, error propagation on non-zero exit). When unconfigured the
hook is a no-op.

Made-with: Cursor

* fix: add prepushScript to run-context API response, fix UI separator

Include prepushScript in the settings returned by the run-context
endpoint so the hook actually fires in production. Also fix the
separator pattern in AgentSettings to match the existing convention
(spacer + hr + spacer instead of margin).

Made-with: Cursor

utils/runContext.ts

@@ -14,6 +14,7 @@ export interface RepoSettings {
   modes: Mode[];
   setupScript: string | null;
   postCheckoutScript: string | null;
+  prepushScript: string | null;
   push: PushPermission;
   shell: ShellPermission;
   prApproveEnabled: boolean;
@@ -33,6 +34,7 @@ const defaultSettings: RepoSettings = {
   modes: [],
   setupScript: null,
   postCheckoutScript: null,
+  prepushScript: null,
   push: "restricted",
   shell: "restricted",
   prApproveEnabled: false,
@@ -93,6 +95,7 @@ export async function fetchRunContext(params: {
         modes: data.settings?.modes ?? [],
         setupScript: data.settings?.setupScript ?? null,
         postCheckoutScript: data.settings?.postCheckoutScript ?? null,
+        prepushScript: data.settings?.prepushScript ?? null,
       },
       apiToken: data.apiToken,
       oss: data.oss ?? false,