Drop EventV2 run facade

[kitlangton]

Summary

• Delete the synchronous EventV2.run facade after migrating call sites to SyncEvent.Service.run.
• Keep EventV2.define as the v2 event schema and SyncEvent-definition builder.

Testing

• bun typecheck from packages/opencode
• bun test --timeout 5000 test/session/compaction.test.ts -t "creates a compaction user message and part"
• bun test --timeout 5000 test/session/processor-effect.test.ts -t "publish retry status updates|capture llm input cleanly"
• bun test --timeout 5000 test/session/prompt.test.ts -t "switch|shell|prompt"
• bunx prettier --check ... for changed files
• bunx oxlint ... for changed files (existing warnings only, no errors)
• pre-push bun turbo typecheck

Stack

1. Use SyncEvent service at event call sites #26782
2. Drop EventV2 run facade #26783 👈 current