Add Slice 4 tuner stack with AGENTS-compliant core types and HTTP API.

Introduces Si4684/ADAU1701 drivers, TunerService, FrequencyKHz,
SeekDirection, /api/tuner routes without file-scope globals, host tests,
and firmware blob tooling (binaries remain gitignored).

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

Software/tools/extract_si4684_blob.py

@@ -0,0 +1,88 @@
+#!/usr/bin/env python3
+"""extract_si4684_blob.py — convert Si4684 C arrays or copies to .bin files.
+
+DigiRadio firmware — https://github.com/manvalan/DigiRadio
+
+Copyright 2026 Michele Bigi
+SPDX-License-Identifier: Apache-2.0
+
+Usage:
+    # From a SigmaStudio-style C header (PE5PVB firmware.h, Si468xROM.h):
+    tools/extract_si4684_blob.py --header src/firmware.h --array firmware \\
+        --out Firmware/Si4684-Firmware/dab_firmware.bin
+
+    # Copy an existing Skyworks .bin from an eval-board folder:
+    tools/extract_si4684_blob.py --copy ~/si46xx_firmware/fm_radio_5_1_0.bin \\
+        --out Firmware/Si4684-Firmware/fm_firmware.bin
+"""
+
+from __future__ import annotations
+
+import argparse
+import re
+import shutil
+import sys
+from pathlib import Path
+
+
+def extract_c_array(header: Path, array_name: str) -> bytes:
+    text = header.read_text(encoding="utf-8", errors="replace")
+    pattern = rf"{re.escape(array_name)}\s*\[\s*\]\s*=\s*\{{(.*?)\}};"
+    match = re.search(pattern, text, re.S)
+    if not match:
+        raise SystemExit(f"array {array_name!r} not found in {header}")
+    values = re.findall(r"0x[0-9a-fA-F]+", match.group(1))
+    if not values:
+        raise SystemExit(f"array {array_name!r} is empty in {header}")
+    return bytes(int(v, 16) for v in values)
+
+
+def extract_flash_region(dump: Path, offset: int, size: int) -> bytes:
+    data = dump.read_bytes()
+    end = offset + size
+    if end > len(data):
+        raise SystemExit(
+            f"flash dump too small: need {end} bytes, have {len(data)}"
+        )
+    return data[offset:end]
+
+
+def main() -> int:
+    ap = argparse.ArgumentParser(description=__doc__)
+    ap.add_argument("--out", type=Path, required=True, help="output .bin path")
+    src = ap.add_mutually_exclusive_group(required=True)
+    src.add_argument("--header", type=Path, help="C header with byte array")
+    src.add_argument("--copy", type=Path, help="existing firmware .bin to copy")
+    src.add_argument("--flash-dump", type=Path, help="full SPI flash dump")
+    ap.add_argument("--array", help="array name when using --header")
+    ap.add_argument(
+        "--offset",
+        type=lambda s: int(s, 0),
+        default=0x106000,
+        help="byte offset for --flash-dump (default: FM region from dirb.tech)",
+    )
+    ap.add_argument(
+        "--size",
+        type=lambda s: int(s, 0),
+        default=0x81721,
+        help="byte length for --flash-dump (default: FM V5.1.0 size)",
+    )
+    args = ap.parse_args()
+
+    if args.header is not None:
+        if not args.array:
+            ap.error("--array is required with --header")
+        payload = extract_c_array(args.header, args.array)
+    elif args.copy is not None:
+        payload = args.copy.read_bytes()
+    else:
+        payload = extract_flash_region(args.flash_dump, args.offset, args.size)
+
+    args.out.parent.mkdir(parents=True, exist_ok=True)
+    args.out.write_bytes(payload)
+    print(f"wrote {args.out} ({len(payload)} bytes)")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())