Add updatable ADAU1701 program via flash partition and HTTP API.

Decouple the SigmaStudio RAM download from compiled-in adau1701_program.c:
DRAD v1 blobs in the dsp partition with embedded fallback, POST /api/dsp/program,
and host-tested blob parse/serialize helpers.

Co-authored-by: Cursor <cursoragent@cursor.com>

Software/tools/pack_dsp_program.py

@@ -0,0 +1,68 @@
+#!/usr/bin/env python3
+"""pack_dsp_program.py — build a DRAD v1 ADAU1701 program blob for POST /api/dsp/program.
+
+Reads a JSON file describing SigmaStudio register writes:
+
+[
+  {"address": 2076, "data": [0, 28]},
+  {"address": 1024, "data": [0, 0, ...]}
+]
+
+Usage:
+  python3 tools/pack_dsp_program.py writes.json -o dsp_program.bin
+"""
+
+from __future__ import annotations
+
+import argparse
+import json
+import struct
+import sys
+import zlib
+from pathlib import Path
+from typing import Any
+
+MAGIC = b"DRAD"
+VERSION = 1
+
+
+def crc32(data: bytes) -> int:
+    return zlib.crc32(data) & 0xFFFFFFFF
+
+
+def pack_writes(writes: list[dict[str, Any]]) -> bytes:
+    payload = bytearray()
+    for entry in writes:
+        address = int(entry["address"])
+        data = bytes(int(x) & 0xFF for x in entry["data"])
+        if not data:
+            raise ValueError(f"empty data at address 0x{address:04X}")
+        payload += struct.pack("<HH", address, len(data))
+        payload += data
+
+    header = bytearray()
+    header += MAGIC
+    header += struct.pack("<HH", VERSION, len(writes))
+    header += struct.pack("<I", crc32(payload))
+    return bytes(header + payload)
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="Pack ADAU1701 DSP program blob")
+    parser.add_argument("json_file", type=Path, help="JSON array of register writes")
+    parser.add_argument("-o", "--output", type=Path, required=True, help="Output .bin")
+    args = parser.parse_args()
+
+    writes = json.loads(args.json_file.read_text(encoding="utf-8"))
+    if not isinstance(writes, list) or not writes:
+        print("JSON must be a non-empty array", file=sys.stderr)
+        return 1
+
+    blob = pack_writes(writes)
+    args.output.write_bytes(blob)
+    print(f"Wrote {len(blob)} bytes to {args.output}")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())