Enable DFlash speculative decoding, remove mlock

- Add --spec-type draft-dflash (was missing, DFlash was inactive)
- Change --load-mode from mlock to none (RLIMIT_MEMLOCK too small for 2.7GB)
- Increase validation max_tokens from 256 to 1024 with complex ML prompt
- Baseline: 18.76 tok/s (was 7.62 tok/s without DFlash)

scripts/serve-llamacpp-dflash.sh

@@ -26,6 +26,7 @@ echo ""
 exec "${SERVER_BIN}" \
     --hf-repo "${TARGET_REPO}" \
     --spec-draft-hf "${DRAFT_REPO}" \
+    --spec-type draft-dflash \
     --spec-draft-n-max "${DRAFT_N_MAX}" \
     --device ROCm0 \
     --spec-draft-device ROCm0 \
@@ -38,4 +39,4 @@ exec "${SERVER_BIN}" \
     --port "${PORT}" \
     --host "0.0.0.0" \
     --threads 16 \
-    --load-mode mlock
+    --load-mode none