feat: implement ramnode/opencode.sh (#812)

Add OpenCode agent script for RamNode Cloud using OpenStack API.

- Use ramnode cloud primitives for server provisioning
- Install OpenCode via opencode_install_cmd helper
- Inject OPENROUTER_API_KEY environment variable
- Launch interactive OpenCode session via SSH

Agent: gap-filler

Co-authored-by: B (Discovery Team) <6723574+louisgv@users.noreply.github.com>

ramnode/opencode.sh

@@ -0,0 +1,45 @@
+#!/bin/bash
+set -eo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" 2>/dev/null && pwd)"
+if [[ -f "${SCRIPT_DIR}/lib/common.sh" ]]; then
+    source "${SCRIPT_DIR}/lib/common.sh"
+else
+    eval "$(curl -fsSL https://raw.githubusercontent.com/OpenRouterTeam/spawn/main/ramnode/lib/common.sh)"
+fi
+
+log_info "OpenCode on RamNode Cloud"
+echo ""
+
+ensure_ramnode_credentials
+ensure_ssh_key
+
+SERVER_NAME=$(get_server_name)
+create_server "${SERVER_NAME}"
+verify_server_connectivity "${RAMNODE_SERVER_IP}"
+wait_for_cloud_init "${RAMNODE_SERVER_IP}" 60
+
+log_step "Installing OpenCode..."
+run_server "${RAMNODE_SERVER_IP}" "$(opencode_install_cmd)"
+log_info "OpenCode installed"
+
+echo ""
+if [[ -n "${OPENROUTER_API_KEY:-}" ]]; then
+    log_info "Using OpenRouter API key from environment"
+else
+    OPENROUTER_API_KEY=$(get_openrouter_api_key_oauth 5180)
+fi
+
+log_step "Setting up environment variables..."
+inject_env_vars_ssh "${RAMNODE_SERVER_IP}" upload_file run_server \
+    "OPENROUTER_API_KEY=${OPENROUTER_API_KEY}"
+
+echo ""
+log_info "RamNode server setup completed successfully!"
+log_info "Server: ${SERVER_NAME} (ID: ${RAMNODE_SERVER_ID}, IP: ${RAMNODE_SERVER_IP})"
+echo ""
+
+log_step "Starting OpenCode..."
+sleep 1
+clear
+interactive_session "${RAMNODE_SERVER_IP}" "source ~/.zshrc && opencode"