Damp hyper-cleaning psi with the current-stage value

[sbryngelson]

The psi damping term in s_compute_rhs read q_prim_vf(psi), the time
stepper's primitive array. That array is only refreshed at the end of
s_compute_rhs, and only when run_time_info, probe_wrt, ib or
bubbles_lagrange is set, so the damping used the previous stage's psi
or, with none of those flags, a never-written array. Toggling
run_time_info changed the solution.

Use q_prim_qp%vf(psi), which aliases the current-stage conservative psi.
run_time_info = T and F now give bit-identical output on a shrunk
2D_orszag_tang_hyper_cleaning case.

Regenerated golden for B4DC99F9 (2D -> MHD -> hyper_cleaning); max
abs deviation 3.9e-4.

[sbryngelson]

Closing this for now to bring the number of open PRs from me down to four, so the ones that stay open get real review attention rather than being lost in a queue of 35.

No work is lost and nothing needs re-doing. The branch fix/hyper-cleaning-psi remains on the fork at 6365acbad4, this PR's diff and discussion stay here, and the head commit is additionally archived in a local verified bundle. Reopening takes no force-push and no rebase:

gh pr reopen 1987 -R MFlowCode/MFC

I intend to reopen these in small batches as the open slots free up. Apologies for the notification noise.

Opened and closed with Claude Code.