Kernel Post Run Endpoint

Accept a full post-run snapshot: evidence values + namespace inventory.

DEPRECATED: only legacy injected Q_VARS clients post here (qualia uses /serialize_and_submit + the inventory Comm). Remove with the local handler and KernelPostRunRequest once the kernel_post_run.start log goes quiet; the drain window is bounded by app-update uptake, not kernel churn.

Internal-principal only: evidence values must originate from the kernel runtime (see VARIABLE_EVIDENCE_INVARIANT).