fuzz: scale iteration count with corpus size

Instead of a fixed 30s run_time, set iterations to 3x corpus size
plus a baseline of 1000. This ensures the full corpus is always
replayed with room for new mutations, while small targets finish
quickly. A 5 minute hard cap prevents any single target from
running too long.

AI tools were used in preparing this commit.

Author: joostjager

fuzz/ci-fuzz.sh

@@ -36,7 +36,8 @@ for TARGET in src/bin/*.rs; do
 	CORPUS_DIR="hfuzz_workspace/$FILE/input"
 	CORPUS_COUNT=$(find "$CORPUS_DIR" -type f 2>/dev/null | wc -l)
 	echo "Fuzzing $FILE (corpus: $CORPUS_COUNT files)"
-	HFUZZ_RUN_ARGS="--exit_upon_crash -n8 --run_time 30"
+	ITERATIONS=$((CORPUS_COUNT * 3 + 1000))
+	HFUZZ_RUN_ARGS="--exit_upon_crash -n8 -N $ITERATIONS --run_time 300"
 	if [ "$FILE" = "chanmon_consistency_target" -o "$FILE" = "fs_store_target" ]; then
 		HFUZZ_RUN_ARGS="$HFUZZ_RUN_ARGS -F 64"
 	fi