fix(test): mock os.platform in ps-based shell detection tests

The 'should use detected shell when ps returns a known shell' and
'should fall back when ps command fails' tests assumed Unix platform.
On Windows CI, getDefaultShell() takes the win32 branch (wmic) instead
of the ps branch, causing the ps mock to be ignored.

Fix: mock os.platform() to return 'linux' so the Unix code path is
always exercised regardless of the CI runner's actual platform.

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

Author: dorlugasigal

test/cli.test.js

@@ -425,8 +425,11 @@ describe('CLI', () => {
 
   describe('getDefaultShell edge cases', () => {
     it('should fall back when ps command fails', () => {
+      const os = require('os');
       const child_process = require('child_process');
+      const origPlatform = os.platform;
       const origExecFileSync = child_process.execFileSync;
+      os.platform = () => 'linux';
       child_process.execFileSync = (cmd, ...args) => {
         if (cmd === 'ps') throw new Error('ps not available');
         return origExecFileSync(cmd, ...args);
@@ -438,13 +441,17 @@ describe('CLI', () => {
         const config = parseArgs();
         assert.ok(config.defaultShell, 'Should have a fallback shell');
       } finally {
+        os.platform = origPlatform;
         child_process.execFileSync = origExecFileSync;
       }
     });
 
     it('should use detected shell when ps returns a known shell', () => {
+      const os = require('os');
       const child_process = require('child_process');
+      const origPlatform = os.platform;
       const origExecFileSync = child_process.execFileSync;
+      os.platform = () => 'linux';
       child_process.execFileSync = (cmd, args, opts) => {
         if (cmd === 'ps') return 'bash\n';
         return origExecFileSync(cmd, args, opts);
@@ -456,6 +463,7 @@ describe('CLI', () => {
         const config = parseArgs();
         assert.strictEqual(config.defaultShell, 'bash');
       } finally {
+        os.platform = origPlatform;
         child_process.execFileSync = origExecFileSync;
       }
     });