refactor: introduce cloud adapter + spawn_agent runner system (#1340)

Eliminate ~70% boilerplate across 149 agent scripts by introducing a
standard cloud_* adapter interface and spawn_agent orchestration runner.

Each cloud's lib/common.sh now exports 7 adapter functions (cloud_authenticate,
cloud_provision, cloud_wait_ready, cloud_run, cloud_upload, cloud_interactive,
cloud_label) that wrap cloud-specific operations behind a uniform interface.

Agent scripts define hooks (agent_install, agent_env_vars, agent_launch_cmd,
etc.) and call `spawn_agent "Agent Name"` — the runner handles the full
deployment flow: auth → provision → wait → install → API key → env → config → launch.

- shared/common.sh: add spawn_agent(), _fn_exists(), _spawn_inject_env_vars()
- 10 cloud lib/common.sh files: add cloud_* adapter functions
- 149 agent scripts: rewrite to hook pattern (~40-80 lines → ~20-35 lines)
- test/run.sh: update 2 sprite test patterns for new adapter paths
- Net reduction: ~4,300 lines (2,257 added, 6,563 removed)

Co-authored-by: lab <6723574+louisgv@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hetzner/opencode.sh

@@ -12,22 +12,8 @@ fi
 log_info "OpenCode on Hetzner Cloud"
 echo ""
 
-# Provision server
-ensure_hcloud_token
-ensure_ssh_key
-SERVER_NAME=$(get_server_name)
-create_server "${SERVER_NAME}"
-verify_server_connectivity "${HETZNER_SERVER_IP}"
-wait_for_cloud_init "${HETZNER_SERVER_IP}" 60
+agent_install() { install_agent "OpenCode" "$(opencode_install_cmd)" cloud_run; }
+agent_env_vars() { generate_env_config "OPENROUTER_API_KEY=${OPENROUTER_API_KEY}"; }
+agent_launch_cmd() { echo 'source ~/.zshrc && opencode'; }
 
-# Set up callbacks
-RUN="run_server ${HETZNER_SERVER_IP}"
-UPLOAD="upload_file ${HETZNER_SERVER_IP}"
-SESSION="interactive_session ${HETZNER_SERVER_IP}"
-
-# Install, configure, launch
-install_agent "OpenCode" "$(opencode_install_cmd)" "$RUN"
-get_or_prompt_api_key
-inject_env_vars_cb "$RUN" "$UPLOAD" \
-    "OPENROUTER_API_KEY=${OPENROUTER_API_KEY}"
-launch_session "Hetzner server" "$SESSION" "source ~/.zshrc && opencode"
+spawn_agent "OpenCode"