fix: migrate core plugins to OpenCode V2

[striderZA]

Summary

• Port CCGSHooks, DriftDetector, and ChangelogGenerator to the OpenCode V2 id/setup(ctx) plugin contract and V2 hook payloads.
• Scope event handling to the plugin project, using envelope/nested location or session.get() when location is omitted.
• Register all three entrypoints under the V2 plugins config key and update core-module copies and plugin documentation.
• Report asset validation failures through the completed tool result instead of throwing from execute.after.

Verification

• node --import tsx --test .opencode/plugins/tests/test-plugin-v2.mjs — 18 passed.
• Bun import check — all six runtime/module plugin exports expose V2 IDs and setup functions.
• git diff --check — clean.

Compatibility and limitations

• V2-only migration, as approved; these plugin implementations no longer support OpenCode 1.x.
• The exact OpenCode 2.0.23 CLI was not available locally (installed CLI is 1.14.33). The migration was checked against the 2.0.23 SDK/schema and tested with Bun.

[Ghostbird]

Solves the issue on my machine. Thanks for the quick reaction!

[striderZA]

Solves the issue on my machine. Thanks for the quick reaction!

Some additional fixes incoming.