The terminal dashboard's builders line says why builders are idle, with the same words as home #7665

Part of #5799.

Done when:

• [ ] The builders line in src/tui/screens/dashboard.ts appends · <word> from idleReason (src/crew/idle_reason.ts) when it is not null.
• [ ] The words are exactly those on home. Import them; never retype them.
• [ ] A terminal test seeds nothing ready with free slots and finds the words on the dashboard. A second test, with every slot busy, finds no reason.

Files: src/tui/screens/dashboard.ts, one test.