Fix platform check for uncompressed data.tar; add CONTEXT.md

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

CONTEXT.md

@@ -0,0 +1,51 @@
+# Current state
+
+Last updated 2026-10-04. `HANDOFF.md` is the brief; this file tracks where the work stands.
+
+## Hardware on hand
+
+Raspberry Pi 4, BrainCraft HAT, Arducam UC-346 camera. Not yet: servos, USB-C splitter, printed
+enclosure, speakers. Work until those arrive is limited to what the Pi, HAT and camera can do.
+
+## Package 0a (platform proof on Ubuntu 24.04)
+
+- **Step 1 done.** `host/check-pi-platform.sh` passes: Ubuntu's `6.8.0-1065-raspi` kernel ships
+  every driver and overlay needed (WM8960 audio, OV5647, Unicam, PWM, SPI, dwc2 gadget with
+  NCM/ECM/ACM). The script needed a fix for uncompressed `data.tar` (applied to `host/` and the
+  duplicate in `tools/`; **uncommitted**).
+- **Step 2 in progress: flashing the SD card.** Image chosen:
+  `ubuntu-24.04.5-preinstalled-server-arm64+raspi.img.xz`, SHA256
+  `b23371a5c8d02f612c26e7c18cacb81c5a48f968c7c66a2645391320aa94351e` (from
+  cdimage.ubuntu.com/releases/24.04/release/SHA256SUMS). It was downloaded to the session
+  scratchpad under `/tmp`, which a reboot likely cleared; re-download and re-verify.
+- The Pi is not running yet. No card has been written. Dev host is NixOS (has `xz`, `dd`,
+  `udisksctl`; no `rpi-imager`).
+- **Open questions for the owner before flashing:** Wi-Fi credentials or Ethernet for first boot;
+  hostname (proposed `hermes-robot`); username; SSH key (default `~/.ssh/id_ed25519.pub`).
+  Plan: write the image after the owner confirms the device from `lsblk`, then edit cloud-init
+  on the `system-boot` partition (user, key, hostname, SSH, network).
+- Remaining 0a steps after boot: ROS 2 Jazzy, audio (`wm8960-soundcard` overlay + mixer),
+  camera (`cam -l`, `camera_ros`), display test pattern. PWM test waits for the servos. Ask
+  before rebooting the Pi.
+
+## Repository
+
+Git repo initialised on `main` with one commit ("Initial commit"). `.gitignore` covers
+`.remember/`, caches, `.venv/`, `*.orig`, `*.rej`. The earlier zip and patch files were deleted.
+`tools/check-pi-platform.sh` duplicates `host/check-pi-platform.sh` and can probably go.
+
+## Security review notes (parked until the USB link is up)
+
+An automated review of the initial commit flagged three items. All stem from the code predating
+the USB-gadget design (HANDOFF.md package 0b); none is exposed until the Pi runs.
+
+- `pi/robot_mcp_server.py`: plain HTTP, `ROBOT_MCP_BIND` defaults to `0.0.0.0`. Plan: default to
+  `10.55.0.2`, start after `usb0`.
+- `pi/pipewire/50-network-server.conf`: TCP 4713 on all interfaces, unrestricted. Plan: keep,
+  comment that the firewall is the protection.
+- `pi/nftables-robot.nft`: still the Pi Zero version (single host IP, any interface). Package 0b
+  rewrites it to accept only on the USB interface from `10.55.0.1`.
+- `pi/install.sh` permissions looked fine (`/etc/robot-mcp.env` is `root:$USER`, 640).
+
+The owner wants to confirm the real IPs on the link before changing any of this. If the USB
+link doesn't work, revisit: TLS or a Tailscale-only bind for MCP and audio.

host/check-pi-platform.sh

@@ -48,6 +48,7 @@ case "$member" in
     *.zst) decomp=(zstd -dc) ;;
     *.xz)  decomp=(xz -dc) ;;
     *.gz)  decomp=(gzip -dc) ;;
+    *.tar) decomp=(cat) ;;
     *)     echo "Unexpected package layout: $member" >&2; exit 1 ;;
 esac
 ar p modules.deb "$member" | "${decomp[@]}" | tar -t > files

tools/check-pi-platform.sh

@@ -48,6 +48,7 @@ case "$member" in
     *.zst) decomp=(zstd -dc) ;;
     *.xz)  decomp=(xz -dc) ;;
     *.gz)  decomp=(gzip -dc) ;;
+    *.tar) decomp=(cat) ;;
     *)     echo "Unexpected package layout: $member" >&2; exit 1 ;;
 esac
 ar p modules.deb "$member" | "${decomp[@]}" | tar -t > files