fix(test): first cross-platform run of the wave's tests — Linux tmp portability + Windows-lane truthfulness

Four platform holes from the lanes' first full run over the v1.67 tests:

- uninstall neutral-root fallback hardcoded /private/tmp (macOS-only) and
  ENOENT'd on Linux CI, where the shard TMPDIR is the gstack-containing
  path that forces the fallback — now realpath'd literal /tmp.
- uninstall's kept-and-listed assertion demanded a backslash path on
  Windows while the bash uninstall prints POSIX paths — now
  separator-insensitive.
- setup-rerun's IS_WINDOWS=0 sub-case and the iron rule's force-restart
  consent path are Unix-shaped by construction (Git Bash ln -snf copies
  without Developer Mode; the consent path boots a real replacement daemon
  the browserless Windows lane cannot host) — gated off win32 with the
  reasons in place; the Windows-relevant halves still run there.
- codex-under-codex-detection drives rendered bash under a hardcoded POSIX
  PATH, so every case saw empty output on Windows — moved to
  KNOWN_WINDOWS_INCOMPATIBLE with the run receipt.

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

scripts/test-free-shards.ts

@@ -169,6 +169,10 @@ export const KNOWN_WINDOWS_INCOMPATIBLE: Array<{ file: string; reason: string }>
   // seven POSIX-bound files the content patterns cannot see (their
   // POSIX-ness is what they TEST, or arrives via a variable). Receipts:
   // PR #2593 windows-free-tests run 31918591602.
+  {
+    file: 'test/codex-under-codex-detection.test.ts',
+    reason: 'drives the rendered preflight bash under a hardcoded POSIX PATH (/usr/bin:/bin) — bash is unreachable through that PATH on Windows, so every case sees empty output (v1.67 windows lane run 95234224148)',
+  },
   {
     file: 'test/regression-pr1169-build-app-sed.test.ts',
     reason: 'tests sed escape sequences in build-app.sh — sed/bash are the subject under test',