Fix SNAC code offset: subtract per-layer offset (position*4096)

SNAC has 3 codebook layers, each 4096 entries. Token position within
the group of 7 determines which layer: pos 0 = L1 (offset 0),
pos 1-2 = L2 (offset 4096), pos 3-6 = L3 (offset 8192).
Without this, codes exceeded 4096 and caused index-out-of-range in SNAC.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

main.py

@@ -237,25 +237,35 @@ def generate_tokens_streaming(text: str, voice: str) -> Generator[str, None, Non
 # ============================================================================
 
 def extract_audio_codes(text_stream: Generator[str, None, None]) -> Generator[int, None, None]:
-    """Extract SNAC audio codes from streamed text. Handles partial tokens across chunks."""
+    """Extract SNAC audio codes from streamed text. Handles partial tokens across chunks.
+    Yields raw token IDs (before layer offset subtraction) — redistribution handles offsets."""
     buffer = ""
+    count = 0
     for chunk in text_stream:
         buffer += chunk
-        # Extract all complete <custom_token_XXXX> patterns
         while True:
             match = re.search(r'<custom_token_(\d+)>', buffer)
             if not match:
                 break
             token_id = int(match.group(1))
             buffer = buffer[match.end():]
-            # Only yield actual audio codes (>= CODE_TOKEN_OFFSET)
             if token_id >= CODE_TOKEN_OFFSET:
-                yield token_id - CODE_TOKEN_OFFSET
+                # Subtract base offset + per-position layer offset (4096 per layer)
+                # Position in group of 7: determines which SNAC layer
+                pos_in_group = count % 7
+                code = token_id - CODE_TOKEN_OFFSET - (pos_in_group * 4096)
+                if 0 <= code < 4096:
+                    count += 1
+                    yield code
+                else:
+                    # Out of range — skip but still count position
+                    count += 1
 
 
 def redistribute_codes(codes: list) -> list:
     """Redistribute flat code list into SNAC's 3 hierarchical layers.
-    Each group of 7: [L1, L2a, L2b, L3a, L3b, L3c, L3d]"""
+    Each group of 7: [L1, L2a, L2b, L3a, L3b, L3c, L3d]
+    Codes are already offset-corrected to 0-4095 range per layer."""
     layer1, layer2, layer3 = [], [], []
     for i in range(0, len(codes), SNAC_CHUNK_SIZE):
         group = codes[i:i + SNAC_CHUNK_SIZE]