feat(a2b): audio — wire play-bgm/play-voice, fix BGM addressing

Wire audio end-to-end (OGG plays natively in Godot; no Frida, no decode):
- IHost.PlayBgm/PlayVoice + VM dispatch for play-bgm(0xbf)/play-voice(0xc4).
  Non-Godot hosts no-op them so --selftest + engine 8/8 stay byte-identical.
- GodotAdvHost resolves id->OGG; Main plays via two AudioStreamPlayer nodes
  (BGM looping; voice interrupt-on-new).

Key finding (by-ear, systematic-debugging): the two audio ops use DIFFERENT
addressing — the earlier "unified manifest" assumption was wrong for BGM.
- play-voice -> per-scene manifest files[base+id] (offset 0, same as textures).
  Confirmed by ear; upgraded med->HIGH.
- play-bgm  -> DIRECT LITERAL NAME BGM{id:03d}.OGG, NOT the manifest.
  Real game: play-bgm 5->BGM005, 8->BGM008 (manifest gave +1). Proven by
  play-bgm 0x23->BGM035 (real standalone track; BGM set skips 030-034) that the
  manifest mis-resolved to a graphics entry. Fix is BGM-only:
  ResourceMap.BgmPathById; voices/textures unchanged.

Also: Lily's silence root-caused as correct form-gating (G[0xa57/0xa58/0xa59]),
left unseeded by choice (no dummy state). Added diagnostic
`Age.Cli audio <SCENE.BIN> [0xADDR=VAL ...]`. Corrected opcodes.toml (play-bgm
direct-name, play-voice HIGH) + docs/memory (dropped the bogus unified-manifest
/ Frida-BGM006 claims).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

godot/GodotAdvHost.cs

@@ -53,4 +53,19 @@ public sealed class GodotAdvHost : IHost
         if (_slotBmp.TryGetValue(slot, out var bmp) && bmp != null)
             _main.CallDeferred("DrawSlot", slot, bmp, dstX, dstY, width, height);
     }
+
+    // ---- audio ops (OGG plays natively in Godot) ----
+    // BGM: addressed by direct name (BGM{id:D3}.OGG), NOT the manifest. Voice: via the per-scene manifest.
+    public void PlayBgm(long id)
+    {
+        var path = _res.BgmPathById(id);
+        if (path != null) _main.CallDeferred("PlayBgm", path);
+    }
+
+    public void PlayVoice(long id)
+    {
+        var asset = _res.Resolve(_scene, id);
+        var path = asset != null ? ResourceMap.AudioPath(asset) : null;
+        if (path != null) _main.CallDeferred("PlayVoice", path);
+    }
 }