llama.cpp slots slash model-switch latency

This is a cache-engineering win, not a model win: once slot state survives process swaps, long-context local agents stop paying the prefill tax every time they come back.

• –The reported speedup comes from KV restore, so it matters most for swap-heavy, context-heavy workflows.
• –The setup is brittle by design: model bytes, context size, quantization, and prompt stability all have to stay fixed or the cache becomes invalid.
• –Hardlinked slot bins plus a supervisor that normalizes prompts turns llama.cpp into something closer to a session manager than a stateless server.
• –The open PRs make this promising evidence, but not yet a polished upstream feature.
• –opencode’s cache-stabilization flag is a practical dependency here because volatile system prompts would otherwise blow the prefix hash.