Investigate and implement fastRoach for UNASSIGNED fibers

UNASSIGNED fibers currently pose a risk during observations, as they may remain at arbitrary positions and potentially hit bright targets. Ideally, these cobras should be hidden behind the black dot, but achieving the required positioning precision is known to be complex and time-consuming.

This ticket proposes investigating and implementing a fastRoach strategy for UNASSIGNED fibers as a safer intermediate solution. The idea is to actively move UNASSIGNED cobras rather than leaving them untouched: first converging them to a predefined safe near-dot location (with careful consideration of possible interference with fiducials), and then driving them open-loop into the black spot.