Fix test: use case-insensitive path check for activate.ps1 on Windows

On Windows, fs.pathExists is case-insensitive so the code may return
'Activate.ps1' even when only 'activate.ps1' exists on disk. The test
assertion should not depend on exact casing of the returned path.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: eleanorjboyd

src/test/managers/common/utils.getShellActivationCommands.unit.test.ts

@@ -110,7 +110,7 @@ suite('getShellActivationCommands', () => {
             assert.strictEqual(pwshActivation[0].executable, '&');
             assert.ok(pwshActivation[0].args);
             assert.ok(
-                pwshActivation[0].args[0].endsWith('activate.ps1'),
+                pwshActivation[0].args[0].toLowerCase().endsWith('activate.ps1'),
                 `Expected path ending with activate.ps1, got: ${pwshActivation[0].args[0]}`,
             );
         });