Add ruleset packs, linter, fixtures, and JSON schema

scripts/generate_fixtures.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+OUT_DIR="$ROOT_DIR/tests/fixtures/generated"
+
+mkdir -p "$OUT_DIR"
+
+ffmpeg -y -hide_banner -loglevel error -f lavfi -i testsrc=size=128x72:rate=30 -f lavfi -i sine=frequency=1000:sample_rate=44100 -t 1 -c:v libx264 -pix_fmt yuv420p -c:a aac -movflags +faststart "$OUT_DIR/clean.mp4"
+ffmpeg -y -hide_banner -loglevel error -f lavfi -i testsrc=size=128x72:rate=30 -f lavfi -i sine=frequency=1000:sample_rate=44100 -t 1 -c:v libx264 -pix_fmt yuv420p -c:a aac "$OUT_DIR/no_faststart.mp4"
+
+# Create a truncated file to simulate partial download/corruption
+cp "$OUT_DIR/clean.mp4" "$OUT_DIR/truncated.mp4"
+python3 - <<'PY'
+import os
+path = "${OUT_DIR}/truncated.mp4"
+size = os.path.getsize(path)
+with open(path, "r+b") as f:
+    f.truncate(max(0, size - 2048))
+PY
+
+echo "Fixtures written to $OUT_DIR"