Selective testing subhashes

The Selective Testing tab on a test run now exposes the same per-target subhashes the Module Cache tab already had. Expand a row to see exactly which inputs went into the hash — sources, dependencies, environment variables, project and target settings, Info.plist, and the rest — making it straightforward to pinpoint the input that drifted when a previously cached test target shows up as a miss. The card also gains a Copy as JSON action that snapshots every selective testing target with its hashes, ready to paste into a ticket or diff against another run.