feat: add user-tweets command to fetch tweets from a user's profile

Adds new CLI command to fetch tweets from any user's profile timeline.

Usage:
  bird user-tweets @username [-n count] [--pages N] [--json]

Features:
- GraphQL UserByScreenName for username → userId resolution
- Cursor-based pagination with configurable delay (rate-limit safe)
- Hard cap of 10 pages to prevent abuse
- Input validation via normalizeHandle()

Includes 17 unit tests and live smoke test.

Co-authored-by: Christian Catalan <[email protected]>

src/lib/twitter-client-constants.ts

@@ -21,6 +21,7 @@ export const FALLBACK_QUERY_IDS = {
   TweetDetail: '97JF30KziU00483E_8elBA',
   SearchTimeline: 'M1jEez78PEfVfbQLvlWMvQ',
   UserArticlesTweets: '8zBy9h4L90aDL02RsBcCFg',
+  UserTweets: 'Wms1GvIiHXAPBaCr9KblaA',
   Bookmarks: 'RV1g3b8n_SGOHwkqKYSCFw',
   Following: 'BEkNpEt5pNETESoqMsTEGA',
   Followers: 'kuFUYP9eV1FPoEy4N-pi7w',