test: forced JVM exit recovery (trasser-jvm-crash-recovery)

Beads trasser-jvm-crash-recovery. Stacked on !72 (merged). Real child JVM + file H2 WRITE_DELAY=0 + JobService: real completed solve, RUNNING at controlled load barrier, QUEUED. Parent kills only child then two new JVMs verify recovery, completed body/export preservation and incomplete export/preview denial. Synthetic leftover files; injected dataset, no HTTP/PostgreSQL/power loss/crash during write. Production unchanged. Maven9/9 PASS, docs1135/1135, catalogue236 valid. Gradle classpath propagation added; Gradle execution awaits CI. Initial test-only numeric representation comparison corrected through store decoder. Push CI skipped to avoid duplicate; MR CI required. No auto-merge.