Implement aios initial direction: AI-managed OS with shared memory

This commit implements the new direction for aios:
- AI conversation interface replaces traditional shell
- aigpt integration for shared memory across containers
- systemd-nspawn for environment isolation

Changes:
- Added aios-install.sh: Complete installer script
- Added cfg/mcp.json: MCP server configuration for aigpt
- Added cfg/config.toml: aios configuration with permission system
- Added cfg/nspawn/aios.nspawn: systemd-nspawn configuration
- Updated build.zsh: Integrated aigpt installation and setup
- Updated README.md: Documented new architecture and philosophy

Architecture:
User → AI Chat → Commands → Execution
         ↓
     aigpt (shared memory)
         ↓
  systemd-nspawn (isolated environment)

Philosophy:
Simply insert AI into existing flows (shell → AI chat)

cfg/mcp.json

@@ -0,0 +1,12 @@
+{
+  "mcpServers": {
+    "aigpt": {
+      "command": "aigpt",
+      "args": ["server", "--enable-layer4"],
+      "env": {
+        "AIGPT_DB": "/root/.config/syui/ai/gpt/memory.db"
+      },
+      "description": "AI memory and personality system"
+    }
+  }
+}