OpenCode 2 support: plugin uses V1-only API, does nothing on V2

Problem

The OpenCode adapter (.opencode/plugins/ponytail.mjs) implements only the V1 plugin API (config hook, experimental.chat.system.transform, command.execute.before, plugin config key).

Per OpenCode's V2 docs, V1 plugin implementations do not run in V2. So on OpenCode 2 the plugin loads but never injects the ruleset or registers the /ponytail commands — V2 users silently get zero ponytail behavior.

Expected

Ship a dual V1+V2 entrypoint from the same file (V1 server() + V2 id/setup(), per the official V1→V2 plugin migration guide) and document the V2 plugins config key:

{ "plugins": ["@dietrichgebert/ponytail"] }

Notes

• V2 mapping: system injection via a context session hook, commands and skills via transforms, one shared mode-flag file so switching OpenCode versions keeps the level.
• I have this working in my fork (shivamnarkar47/ponytail) with tests and can open a PR if wanted.