tests : run test-save-load-state across all architectures
test-save-load-state previously only ran in ctest against a single
downloaded model (tinyllamas/stories15M), i.e. only the llama arch.
Add a --models DIR mode to test-save-load-state that runs the full
save/load suite over every *.gguf in a directory, reporting a
per-model PASS/FAIL and exiting non-zero if any model fails, and wire
a ctest to run it over all architectures using the existing
generate-models fixture (test-llama-archs). The single-model -m mode
is preserved (still used by ci/run.sh).
Also bump the dummy-model training context in test-llama-archs from
128 to 256 so that the per-sequence context (which is padded up to a
multiple of 256) no longer exceeds n_ctx_train and emits the
"possible training context overflow" warning.
The test is expected to fail until the affected arches are fixed:
deepseek4 (host seq-copy), gemma2/gpt-oss/lfm2 (device seq-copy),
minimax-01 (state load). It aborts at the first arch that crashes.
Assisted-by: pi:llama.cpp/Qwen3.8-27B
