docs: add opencode-pilot to ecosystem plugins

[athal7]

Adds opencode-pilot to the ecosystem plugins list.

opencode-pilot is an automation daemon that polls for work from GitHub issues, Linear tickets, and other sources, then spawns OpenCode sessions to work on them. Features include:

• Polling automation from GitHub issues, PRs needing review, Linear tickets
• Readiness evaluation based on labels, dependencies, and priority
• Template-based prompts with customizable placeholders
• Built-in presets for common patterns

Available on npm: npm install -g opencode-pilot