feat(config): add poke strategy

[ngoc-minh-do]

What

Adds the poke strategy — a new GET /api/strategies/poke endpoint that starts instances and immediately returns X-Sablier-Session-Status: ready, skipping the health check. The reverse proxy passes the request through without blocking or showing a waiting page.

Useful when you want instances started but don't need them healthy before serving traffic — background workers, sidecar caches, companion processes the caller doesn't depend on.

Usage

GET /api/strategies/poke?group=myapp&session_duration=30m

Plugin config examples (separate PRs in each plugin repo):

# Traefik
plugin:
  sablier:
    group: myapp
    poke: {}
# Caddy
sablier {
    group mygroup
    poke
}
// Proxy-WASM
{ "group": "mygroup", "poke": {} }