refactor: remove outdated phase summary documents and restructure error handling

- Deleted obsolete phase summary documents (PHASE_1_FIX_SUMMARY.md, PHASE_1_SUMMARY.md, PHASE_2_SUMMARY.md, PHASE_3_SUMMARY.md, PHASE_4_SUMMARY.md, SESSION_HANDOFF.md, TARGET_ARCHITECTURE.md) to streamline documentation.
- Introduced error handling module (error-handler.ts) to centralize error logging and presentation.
- Updated bootstrap and application controller to utilize the new error handling module.
- Refactored runtime provisioning logic into a dedicated module (runtime-setup.ts) for better organization.
- Implemented platform-specific process termination logic in process-killer.ts to enhance process management.
- Enhanced navigation policy with a new module (navigation.ts) to improve URL handling and security.
- Updated window service to integrate new navigation logic for internal and external URL handling.

src/main/nodecg/process-manager.ts

@@ -5,7 +5,7 @@ import path from "node:path";
 
 import { AppRuntimeConfig } from "../config/runtime-config";
 import { NODE_RUNTIME_NAME } from "../constants";
-import { killProcessTree } from "./platform-process-killer";
+import { killProcessTree } from "./process-killer";
 
 type NodecgProcessManagerConfig = {
   isDev: boolean;