chore: stop tracking runtime data directory

data/ was added to .gitignore only after its contents had already been
committed, and an ignore rule never untracks existing files. The live
SQLite database therefore showed up as modified on every commit, made
accidental commits of user history likely, and bloated the repo with
binary churn.

Claude-Session: https://claude.ai/code/session_01QkiLqAtFamcbFXDnCtZSPm

.gitignore

@@ -18,4 +18,4 @@ tmp/
 CLAUDE.md
 .vscode/
 .claude/
-data/
+data/