feat: add OpenCode v2 plugin entrypoint

[peeyush-ciridae]

Summary

• add a native OpenCode v2 entrypoint at opencode-delegated-access/v2
• adapt classification generation, permission evaluation, context hooks, and permission events to the v2 APIs
• preserve the existing v1 entrypoint
• document v2 configuration and add a v2 loader contract test

Validation

• npm run check
• full test suite: 465 tests passed
• package dry run confirmed the v2 entrypoint is published