fix(vscode): include process path env variable in passed path

[benfdking]

• For venvs, we override the PATH env variable, whereas we should be pretending it with the value rather than overriding.

[Copilot]

Pull Request Overview

This PR ensures that the interpreter’s bin directory is prepended to the system PATH when invoking SQLMesh commands, so any required binaries are resolvable at runtime.

• Prepend interpreterDetails.binPath to the existing PATH instead of overriding it
• Applied this change in three execution helpers: getTcloudBin, sqlmeshExec, and sqlmeshLspExec

Comments suppressed due to low confidence (1)

vscode/extension/src/utilities/sqlmesh/sqlmesh.ts:86

• There are no existing tests validating that the PATH string correctly prepends the interpreter bin directory to the original PATH. Consider adding a unit test for the helper (once extracted) to assert this behavior.

      PATH: `${interpreterDetails.binPath!}${path.delimiter}${process.env.PATH || ''}`,