Feature Request: Automatic prompt reloading and project tree caching (by using filesystem watchers)

What feature would you like to see?

Currently, the workflow for using custom prompts and the @ command can be inefficient in two ways:

1. Manual reloading of prompts: after adding a new prompt or modifying an existing one in $CODEX_HOME/prompts/ or ~/.codex/prompts/, I have to restart my codex session for the changes to take effect. This interruption disrupts the development workflow.

1. Slow project tree indexing: the @ command, which is used for context-aware commands, is very slow to execute in large codebases.

I propose two enhancements to address these issues:

1. Implement file system event monitoring for prompts:

• codex should monitor the $CODEX_HOME/prompts/ and ~/.codex/prompts/ directories for any file system events (creation, deletion, modification).

• When a change is detected, codex should automatically rebuild its internal list of available prompts without requiring a manual CLI restart.

1. Cache and incrementally update the project tree:

• On the first run in a new project, codex should build a cache of the project's file tree.

• Subsequently, codex should use file system events to update the cache in the background.

Additional information

_No response_