server : context checkpointing for hybrid and recurrent models (#16382)

* initial commit for branch 3

* generalize `swa_checkpoint` to `ctx_checkpoint`

this extends `llama-server`'s SWA checkpointing logic to include
hybrid/recurrent models such as Jamba, Granite

* oops

* disable debug prints

* keep backwards compat with `--swa-checkpoints`

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

* update prompt re-processing message

* fix off-by-one error per GG

* keep `seq_rm` log per GG

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

* server : fix checkpoint logic to support recurrent caches

* server : cleanup and fixes

---------

Co-authored-by: Georgi Gerganov <ggerganov@gmail.com>

src/llama-model.cpp

@@ -20151,6 +20151,10 @@ bool llama_model_is_recurrent(const llama_model * model) {
     return llm_arch_is_recurrent(model->arch);
 }
 
+bool llama_model_is_hybrid(const llama_model * model) {
+    return llm_arch_is_hybrid(model->arch);
+}
+
 bool llama_model_is_diffusion(const llama_model * model) {
     return llm_arch_is_diffusion(model->arch);
 }