Release fw 0.8.5: BT1035 I2S boot init and hardware doc alignment.

Switch BT1035 bring-up from Line-In to I2S slave (AT+AUXCFG=3, AT+I2SCFG=67) to match the ADAU1701 PCM routing, confirm 2 kΩ I2C pull-ups on R1/R16, and sync firmware docs, AGENTS rules, and the DATASHEET bundle.

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

Hardware/DATASHEET/README.md

@@ -0,0 +1,22 @@
+# Component datasheets (DigiRadio hardware)
+
+Authoritative vendor PDFs used for schematic/PCB design review and firmware
+bring-up. Paths are relative to this repository root (`DigiRadio/`).
+
+| File | Component | Use in DigiRadio |
+|------|-----------|------------------|
+| `SI4684-A10.pdf` | Silicon Labs Si4684-A10 | RSTB power sequencing, SPI framing, supply levels, SMODE |
+| `adau1701.pdf` | Analog Devices ADAU1701 | I²C pull-ups (2 kΩ R1/R16 on PCB; datasheet 2.2 kΩ), MCLK = 256×fS, serial-port master/slave loopback (MP10→MP4, MP11→MP5) |
+| `AN851.pdf` | Silicon Labs AN851 | Si4684 bypass capacitors, antenna layout, schematic guidance |
+| `FSC-BT1035_Datasheet_EN.pdf` | Feasycom FSC-BT1035 | Module pinout, electrical and mechanical specs (v1.0) |
+| `FSC-BT1035_programming_user_guide_1.1.1.pdf` | Feasycom FSC-BT1035 | **AT command reference** — firmware `core::Bt1035At*` maps to §5/§6 |
+
+## Firmware cross-reference
+
+| Manual section | Primary datasheet |
+|----------------|-------------------|
+| `ch-hardware.tex` §validation | `SI4684-A10.pdf`, `AN851.pdf`, `adau1701.pdf`, BT1035 datasheets |
+| `ch-bt1035.tex` §AT commands | `FSC-BT1035_programming_user_guide_1.1.1.pdf` §5 |
+
+When extending BT1035 commands, cite the programming guide section in code comments
+and add a host test in `Software/components/core/test/bt1035_at_test.cpp`.