fix(opencode): Duplicated user request during ACP use

[OpeOginni]

Issue for this PR

Closes #21910

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

fixes an ACP integration bug where OpenCode echoed the user’s live prompt back to the editor as user_message_chunk. We don’t need to send user_message_chunk for a live prompt because the client already has that message

How did you verify your code works?

Created a Custom ACP server with my dev opencode instance and tested this agent and noticed no duplicated user request.

Screenshots / recordings

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Hey! Your PR title Fix/zed acp doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

I found a potentially related PR:

PR #21851: "fix(acp): stop emitting user_message_chunk during session/prompt turn"
#21851

This appears to be directly related to the current PR #22192. Both address the same issue of not emitting user_message_chunk during ACP interactions. You should verify whether PR #21851 already resolves issue #21910 or if it's a different aspect of the same problem that PR #22192 is addressing.