v0.5.5

Fixed

• ai quota statusline-part no longer produces empty output on installations with a legacy quota DB
  that pre-dates AI-CLI-55 (weekly_sonnet_pct column was not migrated via ALTER TABLE, causing a
  silent OperationalError inside the try/except block) (AI-CLI-56).
• _init_db() now calls _migrate_snapshot_columns() to add weekly_sonnet_pct and extra_pct
  to existing quota_snapshots tables that lack them (AI-CLI-56).
• quota_statusline_part() now calls _init_db(conn) on its direct SQLite connection so schema
  migrations always run before any query (AI-CLI-56).
• Statusline bash script quota cache now uses a _quota_cache_valid flag instead of checking
  [[ -z "$quota_part" ]], preventing legitimate empty results from bypassing the 30-second cache
  and triggering repeated blocking calls that produced duplicate prompt boxes in scrollback (AI-CLI-56).