feat(omo-senpi): classify reflection failures for the park policy

classifyReflectionFailure turns a finalization decision into memory-core's
{ fingerprint, retryable } signal: model, auth, ENOENT, sandbox and
validation failures cannot heal on their own and are non-retryable; rate
limits, provider outages, timeouts, parent_dirty and merge_conflict are
retryable. The fingerprint reuses the distilled failure cause so a crash
whose stack frame shifts still counts as the same failure.

Part of #8304