Motir

Estimate: 18m · Depends on: 3.7.3, 3.1.4

Thread the SELECTED board through the read path. Today GET /api/board resolves the active project’s single default board (3.1.6). Generalize: resolve the board from a boardId query param, defaulting to the project’s isDefault board when absent (and 404 if the id isn’t a board of the active project / workspace — never cross-tenant). The board page passes the ?board= selection through; the projection (getBoard), the move, the group-by/WIP config, and the 3.6 column-mapping all already take a boardId — this just makes the SELECTED id flow instead of the implicit default. The swimlaneGroupBy / WIP / columns the UI shows are thus the selected board’s.

Acceptance criteria

• GET /api/board?boardId= returns the named board’s projection; absent → the project’s default board; a board id outside the active project/workspace → 404 (tenant-safe).
• The board page resolves ?board= (default when absent) and every board-scoped call (projection, move, group-by/WIP, column-mapping) uses the selected board id; the single-default path is unchanged when no ?board=.
• Vitest (real Postgres): selecting board A vs B returns each board’s own columns/config; the default fallback; the cross-project/workspace 404.

Context refs

• app/api/board/route.ts (3.1.6 — the active-project board resolution to generalize) + boardsService.getBoard (already boardId-taking, 3.1.4); app/(authed)/boards/page.tsx + BoardContainer.tsx
• Story 3.7.3 (GET /api/boards list) + 3.7.4 (the switcher that sets ?board=)