Add a "Provisioning an SD card" section covering the just init/load/provision
entry points, the config-resolution ladder (env → derive → prompt), the macOS
Keychain Wi-Fi lookup, and the plaintext-secret threat model for the card.
Mark Spike 3 resolved (genuine 32 GB SDHC mounts, round-trips clean on the
shared SPI2 bus; the 133 GB SDXC's CMD59 rejection was the sole fault).
Capture the FatFS f_rename caveat and the ≤32 GB card-compatibility note in
ADR-007, the resolution in the postmortem, and the verified writeup in the
firmware README.
The bench board is a DevKitC-1 v1.0 (RGB LED on GPIO 48), not the v1.1
layout (GPIO 38). Vendor the official v1.0 pinout diagram under docs/ and
reference it from the README so the pinout is pinned offline, and fold in
the 2026-07-04 on-hardware blink verification note.
Generated from esp-rs/esp-idf-template for the ESP32-S3 std target.
src/main.rs toggles GPIO 2 every 500 ms and logs `blink N` over USB-
serial — the minimum bring-up surface called out in
docs/v0.1-mvp-technical.md (Spike 1: confirm toolchain, flash, and basic
GPIO). edition=2024 with rust-version=1.85.
No editor/render/git/usb/fs modules yet; those land per the spike
methodology when later spikes need them.
