feat(tui): relocated terminal restore registration to tui init

- Moved emergency terminal restore registration to the TUI terminal initialization logic.
- Ensured terminal restoration triggers correctly on fatal exits by moving registration out of a side-effect-heavy barrel module.
- Added a registration guard to prevent redundant postmortem handler attachments.

packages/coding-agent/src/modes/index.ts

@@ -1,6 +1,3 @@
-import { emergencyTerminalRestore } from "@oh-my-pi/pi-tui";
-import { postmortem } from "@oh-my-pi/pi-utils";
-
 /**
  * Interactive mode and embeddable RPC client exports for the coding agent.
  *
@@ -11,7 +8,3 @@ import { postmortem } from "@oh-my-pi/pi-utils";
 export * from "./interactive-mode";
 export * from "./rpc/rpc-client";
 export * from "./rpc/rpc-types";
-
-postmortem.register("terminal-restore", () => {
-	emergencyTerminalRestore();
-});