bab3d9078a
Replace synchronous file loading with AppLoadingState state machine (Empty/Loading/Ready/Error) for instant interactivity. Add ViewportCache for on-demand viewport computation, replacing global wrap/level caches. Integrate background indexer polling and file watcher events into the TUI event loop. Add loading UI with progress percentage, estimated line numbers with ~ prefix, and error state display. Eliminate all O(N) linear scans using VisualHeightIndex binary search. Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent) Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>