Retrieve tickets from the board. Accepts an optional `phase` parameter to filter by phase — common filters include 'ready_for_development', 'in_development', 'done', and 'cancelled'. When no phase filter is provided, only active tickets are returned; `done` and `cancelled` tickets are excluded by default. To see completed tickets, pass their phase explicitly (e.g. `phase: "done"` or `phase: "cancelled"`). Use this tool to survey the board state before creating new tickets or updating existing ones, so you can make informed decisions about what work is already in flight. To find archived tickets, use `search_archived_tickets`.