feat(vscode): diagnostic for bad config.yaml error

[benfdking]

• return error
• filter diagnostics so it doesn't show in wrong place

[Copilot]

Pull Request Overview

This PR adds support for reporting and filtering diagnostics when a malformed config.yaml is present in a workspace, ensures the YAML parser is available in tests, and includes a new end-to-end test to cover the invalid-config scenario.

• Add yaml dependency and import execAsync in tests
• Filter LSP diagnostics so only the relevant URI shows the config error
• Track and attach config.yaml path to ConfigError for accurate error location

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

File	Description
vscode/extension/tests/broken_project.spec.ts	New test suite for bad config.yaml handling and error display
vscode/extension/package.json	Added "yaml": "^2.8.0" dependency for YAML parsing in tests
sqlmesh/lsp/main.py	Filter configuration diagnostics by matching the URI value
sqlmesh/core/config/loader.py	Record yaml_config_path and pass it as location in ConfigError

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported

Comments suppressed due to low confidence (1)

vscode/extension/tests/broken_project.spec.ts:316

• The test asserts the error text appears but doesn't verify that the diagnostic is scoped to config.yaml. Consider adding an assertion on the Problems view entry to confirm the file path or URI, ensuring the diagnostic filtering works as intended.

      .isVisible({ timeout: 1_000 })