chore: remove unused root vendor/ directory (215 files from PR #48)

Root vendor/package/ was an accidentally committed extracted npm tarball
(steipete-bird-0.8.0). Zero importers: the real vendored X client lives
at scripts/lib/vendor/bird-search/, referenced by scripts/lib/bird_x.py
and tests/test_bird_x.py.

Removes 215 files + 1 .tgz, dropping repo from 406 to 191 files and
clearing the claude.ai skill-upload 200-file cap.

Adds /vendor/ to .gitignore (leading slash so scripts/lib/vendor/ is unaffected).

.gitignore

@@ -19,3 +19,6 @@ mise.toml
 .venv/
 .coverage
 htmlcov/
+
+# Root vendor/ is accidental - real vendored client lives at scripts/lib/vendor/bird-search/
+/vendor/