feat(vscode): gracefully handle not supported apis

[benfdking]

• test e2e
• test e2e with old version of sqlmesh in environment

[Copilot]

Pull Request Overview

Adds graceful handling for unsupported LSP APIs and backward compatibility with older SQLMesh versions.

• Introduces invalid_state and sqlmesh_outdated error types and handlers in handleError.
• Implements a sqlmesh/supported_methods endpoint plus client-side state to detect unsupported methods.
• Updates command error messages to extract .message from error objects.

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
vscode/extension/src/utilities/errors.ts	Define new error interfaces and handlers (remove merge artifacts)
vscode/extension/src/lsp/lsp.ts	Track supported methods state; update call_custom_method logic
vscode/extension/src/lsp/custom.ts	Add SupportedMethodsMethod to CustomLSPMethods
vscode/extension/src/commands/renderModel.ts	Use .message property on errors for showErrorMessage
sqlmesh/lsp/main.py	Register sqlmesh/supported_methods feature in the LSP server
sqlmesh/lsp/custom.py	Add Pydantic models for supported methods request/response

Comments suppressed due to low confidence (1)

vscode/extension/src/utilities/errors.ts:21

• There are leftover merge conflict markers (<<<<<<<, =======, >>>>>>>) in this file. Please remove them to restore valid syntax.

<<<<<<< HEAD