Use VOL_PROJECTS for project directories across opencode and vscode stacks

- Replace VOL_PATH with VOL_PROJECTS for project mounts
- Remove unused opencode /data volume
- Update sample.env and AGENTS.md with VOL_PROJECTS convention

vscode/compose.yaml

@@ -6,7 +6,7 @@ services:
     restart: ${VSCODE_RESTART:-unless-stopped}
 
     volumes:
-      - ${VOL_PATH:-./data}/vscode/data:/data
+      - ${VOL_PROJECTS:-/data/projects}:/data
       - ${VOL_PATH:-./data}/vscode/config:/config
 
     environment:

vscode/sample.env

@@ -1,5 +1,6 @@
 # ===== Paths =====
 VOL_PATH=/data
+VOL_PROJECTS=/data
 
 # ===== Code Server =====
 VSCODE_IMAGE=lscr.io/linuxserver/code-server:latest