Add 20s long demo audio (en/zh, sampling 0.8/0.95/rep1.1); post_config sampling default for long-text stability

v2 audio fix: RMS-norm fine_local input, zero-pad decoder bits, fix ISTFT log-mag stride; refreshed demo audio (ASR-verified)

Replace with s8 build: LM s8 (Pulsar2 7.0 llm_build2), deterministic greedy generation, refreshed demo audio; drop stale lm_v1_60fix/binaries