Gaps this prototype leaves for the build

1. Every value is mock data. The build reads the agile tree of the work tree the BFF runs in, behind a store interface, and never calls compass.
2. Nothing here writes. Starting, closing and moving a story stay in compass.
3. The sprint is fixed here. The build lists the sprints, and opens the newest by default.
4. The work trees strip needs git worktree list on the server, and reads no other work tree's files.
5. Doc links open inside the tab. The build resolves a link by id and never takes a path from the browser.