chore(opencode-sandbox): fix SSH key permissions and remove read-only flag

.opencode-sandbox/docker-compose.yml

@@ -12,7 +12,7 @@ services:
       # Your monorepo — opencode's working directory
       - /home/ga/workspace:/workspace
       # SSH key for Gitea auth
-      - ~/.ssh/id_ed25519:/root/.ssh/id_ed25519:ro
+      - ~/.ssh/id_ed25519:/root/.ssh/id_ed25519
       - ~/.ssh/known_hosts:/root/.ssh/known_hosts:ro
       # Persist opencode auth so you don't re-login every time
       - opencode-auth:/root/.local/share/opencode

.opencode-sandbox/entrypoint.sh

@@ -1,4 +1,5 @@
 #!/bin/bash
+chmod 600 /root/.ssh/id_ed25519
 export GIT_SSH_COMMAND="ssh -i /root/.ssh/id_ed25519 -o StrictHostKeyChecking=accept-new"
 git config --global user.email "gabriel.pereira@protonmail.com"
 git config --global user.name "gabspereira"