fix(opencode): make bash tool description parameter optional

[RheagalFire]

Issue for this PR

Closes #13618

Type of change

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

What does this PR do?

Claude and other providers reject tool schemas that have properties but no required field with: JSON schema is invalid. It must match JSON Schema draft 2020-12.

Plugin tools like session_list generate schemas with properties but no required. The existing code only handles this for Google/Gemini (filtering required in the Gemini sanitizer). Other providers get
the raw schema and reject it.

The fix adds a recursive ensureRequired pass in transform.ts that sets required: [] on any object schema missing it. Runs before any provider-specific sanitizers so all providers benefit.

How did you verify your code works?

• bun turbo typecheck passes (12/12 packages)
• Husky pre-push hook passes

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:

Found a potentially related PR:

PR #13823: fix: sanitize tool schemas for strict JSON Schema validators (#13737)

• fix: sanitize tool schemas for strict JSON Schema validators (#13737) #13823

This PR appears to be directly related to the current PR (#26420). Both address the issue of invalid tool schemas that fail strict JSON Schema validators. PR #13823 handles schema sanitization for validators that reject schemas with properties but no required field, which is the same core issue being fixed in the current PR.