bug(core): shellExecutionService.windows.integration.test.ts fails on Windows environments without PowerShell 7 (pwsh.exe) #29646

Description

In packages/core/src/services/shellExecutionService.windows.integration.test.ts, the real-shell integration tests are guarded solely with:
`ts
describe.skipIf(!isWindows)
``
However, on standard Windows machines where PowerShell 7 (pwsh.exe) is not installed, getShellConfiguration() falls back to Windows PowerShell 5.1 (powershell.exe).

Because Windows PowerShell 5.1 mangles inline double quotes passed to native executables, 4 out of the 5 tests in the suite fail with exit code 1 (AssertionError: expected 1 to be +0).

As the test suite's docstring explicitly notes:

"These tests exercise the full pipeline end-to-end. They pass when gemini-cli selects pwsh.exe from PATH; they fail when the pipeline routes through Windows PowerShell 5.1."

Steps to Reproduce

1. On a Windows machine where PowerShell 7 (pwsh.exe) is not installed on PATH.
2. Run:
   bash npm test -w @google/gemini-cli-core -- src/services/shellExecutionService.windows.integration.test.ts
3. Observe 4 failing tests.

Proposed Solution

Guard the test suite with: ts const hasPwsh = isWindows && Boolean(resolveExecutable('pwsh.exe')); describe.skipIf(!hasPwsh)(...);

This ensures the suite cleanly skips on Windows installations lacking pwsh.exe, while still running in environments that have PowerShell 7 (such as GitHub Actions CI runners).