perf(tui): cache file-tree flatten/filter/sort between redraws - #94

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: github/codeql-action/analyze@411c4c9a36b3fca4d674f06b6396b2c6d23522c6, github/codeql-action/autobuild@411c4c9a36b3fca4d674f06b6396b2c6d23522c6, github/codeql-action/init@411c4c9a36b3fca4d674f06b6396b2c6d23522c6. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/