Add --stats flag for usage statistics tracking

Track invocations, commands generated/executed, explain calls,
model usage, and interactive sessions. Stats stored in ~/.ask/stats.json
with 100KB size limit and automatic history truncation.

Add spinner for progress feedback and detect project types

Update README.md

Add explain command capability

Relax the update mechanism to do it

only once per 24 hours

Add update file

Add manual and auto-update capability

Initial commit for the ask tool