Fix missing dev-requirements.txt in workspace dependencies list

[Copilot]

Fixes #506

Added an explicit glob pattern *requirements*.txt to ensure requirements files at the workspace root are reliably found. The fix includes:

1. Additional search pattern: Added findFiles('*requirements*.txt') to explicitly search the workspace root
2. Deduplication logic: Implemented deduplication using a Map keyed by file system path to handle overlapping patterns
3. Comprehensive tests: Created 5 new unit tests to validate the fix

Now both patterns work together:

• **/*requirements*.txt - finds requirements files in subdirectories
• *requirements*.txt - finds requirements files at workspace root

Requirements Files Now Discovered

This fix ensures all common requirements file naming patterns are found:

• requirements.txt - main dependencies
• dev-requirements.txt - development dependencies ✨
• test-requirements.txt - testing dependencies ✨
• docs-requirements.txt - documentation dependencies ✨
• prod-requirements.txt - production dependencies ✨
• Any other *requirements*.txt variant ✨

Original prompt

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This section details on the original issue you should resolve

<issue_title>Missing requirements file in workspace dependencies list</issue_title>
<issue_description>I have the following file structure

• click + on venv in environments panel
• click to create environment in root directory
• custom environment
• install workspace dependencies
• I only see requirements.txt as an option

I expect I would see both dev-requirements.txt and requirements.txt because they are both present in the root folder

</issue_description>

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

@eleanorjboyd todo: adopt dev-requirements.txt as something we search in the python environment extension when finding dependency files.

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