feat(vscode): release 0.5.0 project management

[iris-Neko]

Summary

• add blank task creation for Threadbox and official Codex projects
• support official Codex project create, rename, and delete with graceful API fallback
• harden deletion checks, Webview RPC validation, and release workflow behavior
• bump only the VS Code extension to 0.5.0

Verification

• npm run lint
• npm run typecheck
• npm test
• npm run build:vscode
• npm run test:vscode
• npm run package:vscode
• npm run test:cli
• npm run test:cli-package
• npm run test:integration
• npm run test:e2e
• git diff --check

Release

Do not create the vscode-v0.5.0 tag until VSCE_PAT is configured. The tag-triggered workflow publishes VS Code Marketplace and Open VSX before finalizing the GitHub Release.