Make lab coverage accept spec paths and clear stale Gitaly runtime dirs

just lab coverage refused every real spec path: the path check put an escaped bracket inside a bracket expression, which closed the set early. The closing bracket now comes first in the set.

A killed earlier run leaves tmp/run/gitaly-N behind, and the next rspec run dies with gitaly spawn failed. The recipe now clears those directories before it runs, as the dev base guide does by hand.

Proven on a dev rig: the recipe ran two monorepo spec lanes (458 and 397 examples) with coverage and undercoverage to a PASS line.