postcompact-4-probe-quality-check-blocks-resumption-on-failure

PostCompact hook must run 4 verification probes after compaction: Recall (can key facts be recalled?), Artifact (are file paths/function names preserved?), Continuation (can the task continue without re-reading?), and Decision (are architectural choices intact?). Probe failures must block resumption until source files are re-read. Without this gate, sessions resume on degraded context and produce subtly wrong outputs.