[FEATURE]: Allow configuring project-specific LSP servers (e.g., basedpyright instead of pyright) #9472

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Describe the enhancement you want to request

Description:

Currently, OpenCode uses built-in language servers for diagnostics. It would be helpful to allow projects to configure which LSP server to use, so that diagnostics match the project's actual tooling.

Use case:

Our project uses basedpyright (a stricter fork of pyright) for type checking. The built-in pyright sometimes shows different errors or misses issues that basedpyright catches. This leads to a workflow where I have to manually run basedpyright via bash after edits to verify there are no type errors.

Proposed solution:

Allow a configuration option (e.g., in opencode.json or project settings) to specify custom LSP servers per language:

{
  lsp: {
    python: basedpyright
  }
}

The LSP server should be resolved from the project's environment (e.g., virtual environment, node_modules, or PATH) and use the project's configuration files (e.g., pyrightconfig.json, pyproject.toml). This ensures diagnostics respect project-specific settings like strict mode, type checking rules, and import resolution.

This would make the in-editor diagnostics consistent with CI/pre-commit checks and reduce the need for manual verification steps.