ThunderMLX v0.3.2 — rank-symmetric prepare path

Closes an entire distributed wedge class: collectives pair by order across ranks, and the SSD-restore coherence gate ran three all_sums only on ranks whose local cache state took the SSD path — any per-rank cache skew could cross-pair mismatched collectives into a zero-progress pipeline stall (reproduced live before the fix). The prepare phase now issues an identical collective sequence on both ranks under any local cache state: restores are rank-local best-effort reconciled by the unconditional prefix-plan consensus, prepare exceptions vote before aborting so the peer aborts in lockstep, the image cache gate keys on a symmetric any-rank-has-image exchange, prewarm cleanup is symmetric, and divergences self-heal by re-aligning per-rank SSD artifacts instead of looping. Enables the admission guard's full eviction ladder, including live-cache release under memory pressure.