test(python): mock process.platform to make marker tests cross-platform

PEP 508 marker tests assume a Linux/POSIX environment. On Windows,
the marker evaluator would include win32-gated packages, causing
fixture mismatches. Override process.platform to 'linux' for the
duration of the test suite so results are deterministic on any OS.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: ruromero

test/providers/python_pyproject.test.js

@@ -9,6 +9,7 @@ import Python_poetry from '../../src/providers/python_poetry.js'
 import Python_uv from '../../src/providers/python_uv.js'
 
 let clock
+let originalPlatform
 
 const TIMEOUT = process.env.GITHUB_ACTIONS ? 30000 : 15000
 
@@ -590,4 +591,11 @@ suite('testing the python-pyproject data provider', () => {
 		})
 	})
 
-}).beforeAll(() => clock = useFakeTimers(new Date('2023-10-01T00:00:00.000Z'))).afterAll(() => clock.restore())
+}).beforeAll(() => {
+	originalPlatform = process.platform
+	Object.defineProperty(process, 'platform', { value: 'linux', configurable: true })
+	clock = useFakeTimers(new Date('2023-10-01T00:00:00.000Z'))
+}).afterAll(() => {
+	Object.defineProperty(process, 'platform', { value: originalPlatform, configurable: true })
+	clock.restore()
+})