fix: improve Slack support and fix Windows community plugin installer…

[adambeazley]

… crash

Summary

This PR improves support for the Slack adapter on Windows and makes community channel adapters more reliable when installed manually.

Related Issues

• The openacp install command was crashing on Windows with a libuv assertion error (UV_HANDLE_CLOSING).
• Slack was not treated as a first-class channel, which caused issues when people had to manually install the adapter (common on Windows).
• Manually installed channel adapters were not being fully initialized by the core.

Type of Change

• [ X ] 🐛 Bug fix
• [ X ] ✨ New feature
• 🔌 New adapter / plugin
• 📝 Documentation
• ♻️ Refactor (no functional change)
• ⚡ Performance improvement
• 🧪 Tests
• 🔧 CI / Build / Config

Changes Made

• Replaced fragile execFile usage with a more robust spawn-based npm install in the plugin installer (fixes the Windows crash).

• Added proper first-class Slack support (CHANNEL_META, status reporting, and configuration flow).

• Improved handling for manually installed channel adapters so they get better recognized during boot.

Testing

• Ran pnpm test — all tests pass
• [ x ] Tested manually with:
• Tested on Windows where the installer was previously crashing.
• Claude now warm-pools reliably.
• Manual Slack adapter installation no longer leaves the adapter in a half-initialized state.
• Added new tests for this change
• No tests needed (explain why)

Platform Impact

• Telegram
• Discord
• Slack
• CLI
• REST API
• Web UI
• All / Core

Screenshots / Recordings

Checklist

• My code follows the project's TypeScript conventions (ESM, .js extensions)
• I have updated relevant documentation (if needed)
• I have added/updated tests (if applicable)
• My changes don't introduce new warnings or errors
• I have run pnpm build successfully
• My changes are backward compatible with existing config and data formats
• If changing plugin API / PluginContext: I have updated src/cli/plugin-template/