Persist last displayed tweet lists and allow opening a tweet by index.
- Add twitter_cli/cache.py: stores a short-index cache (~/.twitter-cli/last_results.json) with a 1h TTL and helpers to resolve index->tweet-id and cache size.
- Update twitter_cli/cli.py: save list results to cache, display a hint, and add `twitter show <N>` command which fetches a tweet by cached index and prints detail/replies (supports --full-text, --json, structured output, and max replies).
- Update README.md and SKILL.md to document the new `show` usage.
- Add .idea/ to .gitignore and bump package version in uv.lock to 0.8.0.
This change makes it easy to open items from the last feed/search without copying IDs.
