fix(opencode): show CLI failure message before help

[fancive]

Issue for this PR

Closes #29390

Type of change

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

What does this PR do?

When yargs reports an invalid CLI argument, the top-level .fail() handler showed the full help text but did not print the failure message. That made opencode --unkown-flag look the same as opencode --help.

This change prints the yargs failure message with the existing CLI error formatter before rendering help. It keeps the existing help behavior while making invalid arguments visible to the user. A subprocess regression test covers the invalid-argument path and checks that the error appears before the help command list.

How did you verify your code works?

• bun test test/cli/fail-help.test.ts from packages/opencode
• bun typecheck from packages/opencode
• npm run lint fallback at repo root: 3537 warnings, 0 errors
• pre-push hook: bun turbo typecheck passed

Screenshots / recordings

Not applicable. This is CLI stderr output.

Checklist

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

[github-actions]

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

Potential Duplicate Found:

• PR fix(opencode): show error message in CLI .fail() handler #29393: fix(opencode): show error message in CLI .fail() handler
  • fix(opencode): show error message in CLI .fail() handler #29393

This PR appears to be addressing the same issue—showing error messages in the CLI .fail() handler instead of silently showing help. It may have been closed or superseded, or it could be the earlier attempt at fixing the same root cause that issue #29390 references.

I recommend checking PR #29393 to see if it's still active or if the current PR #31228 is an improved version of that work.

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍

[github-actions]

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