fix(npu fetch): never resume into a file from another revision

A version bump re-cuts the device programs, so a staged file of a different
size is stale rather than partial. `curl -C -` against it appended the new
tail to the old bytes and produced the right BYTE COUNT with the wrong
content — the sha256 gate caught it (consts.hnpb, 2026-10-30), and the
failure reads as a corrupt program rather than a fetch fault. Resume only
when the staged file is smaller than the manifest expects.

scripts/download-frank-dragoon-npu.sh

@@ -105,7 +105,18 @@ for MODEL in ${MODELS//,/ }; do
                 # 62 GiB fetch hit this on 2026-10-18).
                 url=$(curl -sfIL -o /dev/null -w '%{url_effective}' "$HF/$NPU_REPO/resolve/$NPU_REV/$f") \
                     || { echo "cannot resolve $NPU_REPO/$f" >&2; exit 1; }
-                curl -fL --retry 5 -C - -o "$path" "$url"
+                # Resume ONLY into a genuinely partial file. A staged file of a
+                # DIFFERENT size is an artifact of another revision (a version
+                # bump re-cuts the device programs), and `-C -` against it
+                # appends the tail to the old bytes: the result is the right
+                # BYTE COUNT with the wrong content, which reads as a corrupt
+                # program, not as a fetch fault (measured 2026-10-30 on
+                # consts.hnpb). Fetch those from zero.
+                resume=()
+                if [ -f "$path" ] && [ "$(stat -c %s "$path")" -lt "$want" ]; then
+                    resume=(-C -)
+                fi
+                curl -fL --retry 5 "${resume[@]+"${resume[@]}"}" -o "$path" "$url"
             fi
         fi
         [ -f "$path" ] || { echo "MISSING $path (run without --verify-only)" >&2; exit 1; }