Fix DeepCompile profiling memory cleanup

[tohtana]

This PR reduces DeepCompile ZeRO-3 memory pressure in profiling and compiled backward by fixing three related issues:

• Let the partitioner keep using its min-cut rematerialization policy for non-parameter activations, while still forcing ZeRO-3 parameter aliases/casts to be recomputed.
• Compute selective-gather persistence capacity from profiled transient headroom instead of current allocator availability.
• Avoid retaining temporary profiling outputs across warmup/measured profiling iterations, and clear gathered ZeRO-3 parameters when profiling exits through an exception.
• Mark incomplete memory profiles explicitly, synchronize the completion status across ranks, and skip profile-dependent prefetch/selective-gather decisions when profiling data is incomplete.

[PKUWZP]

LGTM, approved.