Clean out the Pi Zero leftovers, rewrite the README, and add the one installer

Wi-Fi-off acceptance passed: with Wi-Fi blocked, live and after a reboot, the Pi
came up on the USB link alone, every node ran, and hermes mcp test robot and look()
worked. (A temporary guard that would have unblocked Wi-Fi was the safety net and is
removed; Wi-Fi is back on.)

Delete what the ROS design superseded: the Picamera2 MCP server and its unit, the old
installer and requirements, and the duplicate platform check. Move omarchy/ to
host/omarchy/. Rewrite README.md for this build: parts, physical steps (including the
Audio switch), setup, daily use, the troubleshooting learned the hard way, and the
security model.

pi/install.sh is now the single installer for a fresh Ubuntu 24.04 image, built from the
steps done by hand: ROS, the libcamera fork at a pinned commit, camera_ros, the venv and
models, the workspace, USB gadget, audio overlay, firewall (before PipeWire opens a
port), PipeWire, mixer and services. Run twice on the live robot, the second run changed
nothing and everything stayed healthy. It has not been run on a blank card.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AFN8nRRCiDiMN7ChBpHJhs

CLAUDE.md

@@ -8,11 +8,13 @@ the Pi; on the hosts, ROS runs only in podman containers.
 **Start with `HANDOFF.md`.** It is the implementation brief: hardware facts, what exists, the
 work packages in order, acceptance checks, and the list of unverified assumptions.
 
-- `pi/` and `ros/` run on the robot; `omarchy/` (to become `host/`) runs on the owner's machines.
+- `pi/` and `ros/` run on the robot; `host/` runs on the owner's machines. `CONTEXT.md` tracks where
+  the work stands; `HANDOFF.md` is the original brief and has drifted (ROS stays on the Pi, and
+  `hermes_mcp` is the only bridge out; see `CONTEXT.md`).
 - Package 0a (platform proof) comes before everything; start with `host/check-pi-platform.sh`.
 - `docs/face-prototype.html` is the reference for the face renderer; port it, don't ship it.
 - `enclosure/` holds the OpenSCAD model and STLs. It was built from estimates; refine it from the
   owner's caliper measurements and test prints before anyone prints the large parts.
-- `README.md` still describes the earlier Pi Zero build until package 7 rewrites it.
+- `README.md` is the guide for this build; keep it a guide for a person, and keep `CONTEXT.md` honest.
 - The MCP server uses the MCP Python SDK 2.x (`mcp.server.mcpserver.MCPServer`), not 1.x `FastMCP`.
 - Ask before rebooting the Pi, upgrading or holding kernel packages, or opening network ports.