Add ruleset packs, linter, fixtures, and JSON schema

rulesets/codecs-audio.toml

@@ -0,0 +1,29 @@
+[[rule]]
+id = "AAC_ADTS_HEADER_ERROR"
+domain = "codec.aac"
+severity = "medium"
+confidence = 0.7
+fix_tier = "reencode"
+stop_scan = false
+patterns = ["(?i)Error parsing ADTS frame header", "(?i)Error decoding AAC frame header"]
+notes = "AAC bitstream errors detected."
+
+[[rule]]
+id = "MP3_HEADER_MISSING"
+domain = "codec.mp3"
+severity = "medium"
+confidence = 0.6
+fix_tier = "reencode"
+stop_scan = false
+patterns = ["(?i)Header missing"]
+notes = "MP3 framing errors detected."
+
+[[rule]]
+id = "AC3_FRAME_SYNC_ERROR"
+domain = "codec.ac3"
+severity = "medium"
+confidence = 0.6
+fix_tier = "reencode"
+stop_scan = false
+patterns = ["(?i)frame sync error"]
+notes = "AC-3 frame sync error detected."