test(startup): pin the platform in the probe-env test

shellProbeEnv short-circuits on win32, so the POSIX-only assertion failed
for anyone running the suite on Windows. Matches the convention in
hydrate-shell-path.windows.test.ts.

Also narrows the win32 exemption comment: WindowsShellPathOwnership
snapshots its baseline after the seeds land, so it does not unwind them.
The exemption holds because Windows keys PATH as `Path` and no Windows
seed pins a node version.

src/main/startup/hydrate-shell-path.test.ts

@@ -40,6 +40,7 @@ describe('hydrateShellPath', () => {
   })
 
   afterEach(() => {
+    vi.restoreAllMocks()
     if (originalPath === undefined) {
       delete process.env.PATH
     } else {
@@ -180,6 +181,9 @@ describe('hydrateShellPath', () => {
   })
 
   it('probes with the recorded launch PATH so seeded fallbacks cannot pin nvm', async () => {
+    // Why: shellProbeEnv short-circuits on win32, so pin the platform or this
+    // POSIX-only assertion fails for anyone running the suite on Windows.
+    vi.spyOn(process, 'platform', 'get').mockReturnValue('darwin')
     const proc = createMockShellProcess()
     spawnMock.mockReturnValue(proc)
     process.env.PATH = `/home/u/.nvm/versions/node/v26.7.0/bin${delimiter}/usr/bin`

src/main/startup/hydrate-shell-path.ts

@@ -36,8 +36,8 @@ let probeQueue = Promise.resolve()
 // ahead of PATH before we probe. nvm's startup `use` honors whatever node is
 // already on PATH over the user's `default` alias, so a probe that inherits the
 // seed comes back pinned to that version and every terminal loses the global
-// CLIs installed under `default`. Probe with the launch PATH; Windows gets the
-// same protection from WindowsShellPathOwnership.
+// CLIs installed under `default`. Probe with the launch PATH instead. win32 is
+// exempt: it keys PATH as `Path`, and no Windows seed pins a node version.
 let launchPath: string | null = null
 let configuredWindowsShell = 'powershell.exe'
 let configuredWindowsGitBashPath: string | null = null