Add unit tests for envFile trailing comment handling

[Copilot]

User reported that FOO=bar # trailing comment in .env files was including the comment in the value. Investigation confirmed the current dotenv 16.4.5 dependency handles inline comments correctly (support added in v15.0.0).

Changes

• Added comprehensive unit tests for parseEnvFile and mergeEnvVariables in envVarUtils.ts
• Tests verify trailing comments are stripped from unquoted values
• Tests verify hash characters inside quotes are preserved (expected behavior)
• Edge cases covered: empty files, CRLF line endings, export prefixes, multi-line configs

Test Coverage

// Trailing comments stripped
'FOO=bar  # comment' → { FOO: 'bar' }

// Hash preserved in quotes
'FOO="bar  # not a comment"' → { FOO: 'bar  # not a comment' }

The reported issue may have been a regression in an older extension version or a quoted value scenario. These tests prevent future regressions.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>envFile configuration wrongly includes a trailing comment in environment variable value</issue_title>
<issue_description># Description
I defined an environment variable with a trailing comment in my .env file.

FOO=bar  # trailing comment

When debugging the following python module.

import os

foo = os.getenv("FOO")
print(foo)

foo gets value bar # trailing comment, the expected behaviour is foo has value bar.

Version

I am using MacOS and I have the following extensions:

Name: Python Environments
Id: ms-python.vscode-python-envs
Description: Provides a unified python environment experience
Version: 1.12.0
Publisher: Microsoft
VS Marketplace Link: https://marketplace.visualstudio.com/items?itemName=ms-python.vscode-python-envs

Name: Python Debugger
Id: ms-python.debugpy
Description: Python Debugger extension using debugpy.
Version: 2025.16.0
Publisher: Microsoft
VS Marketplace Link: https://marketplace.visualstudio.com/items?itemName=ms-python.debugpy

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes envFile configuration wrongly includes a trailing comment in environment variable value #1014

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.