Fix Windows CI: assert path shapes with either separator

The one failing test, "the host location is named per platform", asked
hostDataDir for the macOS answer and then demanded forward slashes of it.
But path.join always joins with the separator of the machine it is running
on — the platform argument chooses the folder NAMES, nothing more — so on
the Windows runner the answer reads \Users\x\Library\Application
Support\TreeMap: right names, host separators, failed pattern.

Pre-existing, not from this branch: the Tests runs on 931aeb0 and 5f99e8b
were already red on Windows with this same single test (confirmed via the
public check-run annotations). The previous session guarded two D3 tests
for Windows but this third one only surfaced in a run that finished after
its final push. macOS and Linux stayed green throughout.

The pattern now accepts either separator; behaviour is untouched.

Suite 828 (826 pass, 2 platform skips) locally.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: Prithvi-Web

HANDOFF.md

@@ -300,7 +300,11 @@ B5 zombie handles.
 - Windows-host rules that ARE code rules: sanitizers `path.resolve()` requests,
   so fixtures live at `path.resolve('/root')`; test after()-hook `rmSync` needs
   `maxRetries/retryDelay`; async work must re-check `db === handle` after every
-  await.
+  await. And **`path.join` always joins with the HOST's separator**, even when
+  building another platform's folder names — assert path shapes with `[\\/]`,
+  never a literal `/`. (This one broke Windows CI from the D3 commit until
+  29 Jul: the previous session guarded two D3 tests but this third one only
+  surfaced after its push, in a run nobody was left to read.)
 
 ---
 

tests/portableMode.test.ts

@@ -232,7 +232,12 @@ test('the boot volume is never offered as an external drive', () => {
 });
 
 test('the host location is named per platform so the UI can say what is avoided', () => {
-  assert.match(hostDataDir('darwin', '/Users/x'), /Library\/Application Support\/TreeMap$/);
+  // What the platform argument chooses is the FOLDER NAMES; the separators
+  // always belong to the machine the code is running on, because path.join
+  // joins with the host's own. So on the Windows CI runner the darwin answer
+  // reads `\Users\x\Library\Application Support\TreeMap` — right names, host
+  // separators — and a forward-slash-only pattern failed there for months.
+  assert.match(hostDataDir('darwin', '/Users/x'), /Library[\\/]Application Support[\\/]TreeMap$/);
   assert.match(hostDataDir('linux', '/home/x'), /treemap$/);
   assert.ok(hostDataDir('win32', 'C:\\Users\\x').includes('TreeMap'));
 });