build: make GitHub archive fallback resumable

Download archive into .part, validate with gzip -t, retry, then extract. Helps on flaky TLS connections.

scripts/general.sh

@@ -365,12 +365,32 @@ fetch_from_github_archive()
 	local tar_url="${base}/archive/refs/heads/${ref_name}.tar.gz"
 	local archive_dir="${EXTER}/cache/sources/.github-archives"
 	local tar_path="${archive_dir}/$(basename "${base}")-${ref_name}.tar.gz"
+	local tar_part="${tar_path}.part"
 
 	mkdir -p "${archive_dir}" || return 1
 
 	display_alert "Downloading GitHub archive" "${tar_url}" "wrn"
-	# -c enables resume; keep a cached tarball in EXTER/cache/sources
-	wget -q -c -t 10 --timeout=30 --waitretry=5 -O "${tar_path}" "${tar_url}" || return 1
+	local attempt
+	for attempt in 1 2 3; do
+		# Resume into a .part file, verify integrity, then promote.
+		if command -v curl >/dev/null 2>&1; then
+			curl -L --fail --retry 10 --retry-delay 5 --connect-timeout 30 \
+				--continue-at - -o "${tar_part}" "${tar_url}" || true
+		else
+			wget -c -t 10 --timeout=30 --waitretry=5 -O "${tar_part}" "${tar_url}" || true
+		fi
+
+		if gzip -t "${tar_part}" >/dev/null 2>&1; then
+			mv -f "${tar_part}" "${tar_path}" || return 1
+			break
+		fi
+
+		display_alert "Archive download incomplete; retrying" "attempt ${attempt}/3" "wrn"
+		rm -f "${tar_part}" 2>/dev/null || true
+		sleep 5
+	done
+
+	[[ -f "${tar_path}" ]] || return 1
 
 	display_alert "Extracting archive" "${workdir}" "wrn"
 	mkdir -p "${workdir}" || return 1