fix: align waits runtime with OpenCode beta-19242

[davidprokopec]

Summary

• Fix server activation crash caused by Effect beta.107 receiving an rc.112 Scope (single-finalizer state has no finalizers Map).
• Align plugin/schema/theme, Effect, and OpenTUI dependencies with OpenCode beta-19242; prepare version 0.2.1.
• Migrate optional server template commands to the executable command API, preserving argument text, attachments, delivery, and errors.
• Document compatibility and verified local loading instructions.

Verification

• Bun 1.3.14: typecheck, lint, 84 tests pass.
• Reproduced the exact original crash in an isolated beta-19242 server with the old cached package.
• npm-packed artifact installed with npm and loaded via its server export in an isolated beta-19242 server: active, all three optional commands registered.
• Independent review completed; corrected stale README compatibility version.
• Original uncommitted checkout changes are excluded.