feat: add ofxpimapper-full-stack OpenSpec artifacts

Comprehensive blueprint for a headless Raspberry Pi 3B projection mapping appliance:
- Unified installer with 2GB swap safety for C++ source builds.
- WebSocket-driven real-time vertex/surface manipulation.
- 5-tab responsive dashboard (Dashboard, Mapping, Media, Network, System).
- Media validation with ffprobe (H.264 check) and resource warnings.
- Throttled log streaming and explicit mapping persistence.

openspec/changes/ofxpimapper-full-stack/proposal.md

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+## Why
+
+Currently, setting up a Raspberry Pi for projection mapping requires manually piecing together the OS, the mapping engine (`ofxPiMapper`), and various control scripts. This is fragmented, difficult to manage headlessly, and lacks a modern "appliance" feel. `ofxpimapper-full-stack` aims to unify these into a single, polished, and professional product: the Modern PocketVJ (MPVJ). It provides an "it just works" experience for artists, from the initial setup script to the real-time web-based mapping remote.
+
+## What Changes
+
+- **Unified Headless Installer**: A single setup script that installs the entire stack, including the `ofxPiMapper` engine, Node.js backend, and React frontend.
+- **Integrated Mapping Engine**: Automated installation of `ofxPiMapper` (pre-compiled binary or source build) with a systemd service to launch fullscreen on boot.
+- **Virtual Canvas 2.0**: A responsive React/Tailwind web UI for real-time vertex/surface manipulation via WebSockets, with live feedback on the beamer.
+- **Enhanced Media Vault**: Complete media management (upload/delete/preview) with the ability to assign different sources (video/image/color) to individual surfaces.
+- **Appliance Dashboard**: Integrated monitoring of system health (CPU, RAM, Temp) and process status, with remote power and restart controls.
+- **Hybrid Networking**: A robust networking stack that maintains a permanent Access Point while allowing connection to external venue WiFi via a web interface.
+
+## Capabilities
+
+### New Capabilities
+- `ofxpimapper-engine`: The core C++ mapping engine, integrated into the system-wide process management.
+- `web-remote-dashboard`: A modern, responsive TUI-inspired web interface for full system control.
+- `media-source-assignment`: The ability to dynamically map specific files or colors to specific geometric surfaces.
+- `live-logs-streaming`: Real-time streaming of system and mapper logs to the web interface.
+
+### Modified Capabilities
+- `headless-installer`: Upgraded to handle the C++ engine installation and graphics driver configuration.
+- `osc-bridge-api`: Expanded to handle naming, surface selection highlighting, and source assignment.
+- `hybrid-network-control`: Updated with a scan-and-connect web UI while preserving the AP.
+
+## Impact
+
+- **Hardware**: Strictly optimized for the Raspberry Pi 3B (1GB RAM).
+- **User Experience**: Transition from a "CLI-first" or "Desktop-first" workflow to a "Web-Remote-first" workflow.
+- **Performance**: Heavy reliance on WebSockets and optimized C++ binaries to ensure low-latency interaction.
+- **Stability**: Automated swap management and process monitoring to prevent OOM crashes during high-resolution playback.