feat(inference): cap consecutive SeaCache reuses

[lfengad]

Summary

Sync the SeaCache consecutive-reuse cap from imaginaire4!12068 into the OSS inference stack.

• tune the default diffusion-cache threshold from 0.35 to 0.25
• cap consecutive cached residual reuses at 2 by default, per CFG pathway
• expose diffusion_cache_max_consecutive_cached through setup overrides (0 disables the cap)
• forward the override into DiffusionCache.Config and include the effective value in startup logging
• add OSS-path coverage for config validation, state-machine behavior, argument round-trip, and inference forwarding

The production behavior matches the i4 MR; paths and tests are adapted to the OSS repository layout.

Testing

Not run, per request. Static diff and control-flow review completed; git diff --check passes.