Step 7.3: decode HLS TS segments to PCM (own TS demux + AAC decoder)

- main/decoder: MPEG-TS demux (packets reassembled across HTTP chunks,
  PAT -> PMT -> first ADTS-AAC PID, PES headers stripped) feeding the
  esp_audio_codec simple AAC decoder (ADTS, AAC-Plus enabled for HE-AAC
  v1/v2 variants). 7.3 only counts and logs PCM per segment.
- esp_audio_codec pinned to ~2.5.0: 2.6+ needs P4 rev >= 3 (this board
  is rev 1.3). Noted in CLAUDE.md, also for esp_audio_effects < 1.4.
- The library's combined TS decoder lost ~8% of the frames (segments
  decoded to 7.9-9.6 s, "decode error -1"); with the own demux every
  segment is sample exact: 441344 / 440320 frames = 10.008 / 9.985 s,
  matching EXTINF 10.0078 / 9.9846 (431 / 430 AAC frames), no errors.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

main/decoder.h

@@ -0,0 +1,12 @@
+// Decoder for HLS segments (MPEG-TS with AAC-LC / HE-AAC), fed by the HLS client's sink.
+#pragma once
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include "esp_err.h"
+
+esp_err_t decoder_init(void);
+// hls_sink_t: segment bytes in; PCM out (7.3: counted and logged).
+bool decoder_feed(const uint8_t *data, size_t len, bool segment_start);