Adds --debug-tap <room> flag (or debug_tap in TOML config) that logs
every media packet's header metadata passing through a room. Use '*'
for all rooms.
Output (via tracing target "debug_tap"):
TAP room=... dir=in addr=... seq=31 codec=Opus24k ts=520
fec_block=5 fec_sym=1 repair=false len=65 fan_out=1
Shows: direction, source address, sequence number, codec ID, timestamp,
FEC block/symbol, repair flag, payload size, and fan-out count.
No decryption needed — headers are not encrypted.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>