OpenCode's copilot fetch wrapper already sets x-initiator based on the
actual HTTP request body content. When oh-my-opencode's chat.headers
hook overrides it with 'agent', the Copilot API detects a mismatch
between the header and the request body and rejects the request with
'invalid initiator'.
This matches the approach OpenCode's own chat.headers handler uses
(copilot.ts:314) — it explicitly skips @ai-sdk/github-copilot models
because the fetch wrapper handles x-initiator correctly on its own.
Remove duplicated dispatchToHooks declaration that broke TypeScript parsing, and isolate chat-headers tests from marker cache collisions with unique message IDs.
