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

mcp/git.ts

@@ -2,6 +2,7 @@ import { regex } from "arkregex";
 import { type } from "arktype";
 import { log } from "../utils/cli.ts";
 import { $git } from "../utils/gitAuth.ts";
+import { executeLifecycleHook } from "../utils/lifecycle.ts";
 import { $ } from "../utils/shell.ts";
 import type { StoredPushDest, ToolContext } from "./server.ts";
 import { execute, tool } from "./shared.ts";
@@ -143,6 +144,8 @@ export function PushBranchTool(ctx: ToolContext) {
         ? ["--force", "-u", pushDest.remoteName, refspec]
         : ["-u", pushDest.remoteName, refspec];
 
+      await executeLifecycleHook({ event: "prepush", script: ctx.prepushScript });
+
       log.debug(`pushing ${branch} to ${pushDest.remoteName}/${pushDest.remoteBranch}`);
       if (force) {
         log.warning(`force pushing - this will overwrite remote history`);