fix: round-6 CI backlog (32 python, docker arm64, win32-arm64, windows lane, desktop lint)

- pm.environment: the `--no-install-package <name>` root read parses [project].name without
  tomllib on the pre-3.11 bootstrap python (Docker arm64 stage_runtime). Both parsers proven
  to agree on the real pyproject.
- windows-build-deps.ps1 / run_tests.sh: with DISTUTILS_USE_SDK, setuptools takes link.exe
  from PATH; under a bash-hosted step Git for Windows' coreutils `link` shadowed MSVC's.
  The MSVC linker directory now leads PATH (cl.exe was already found — this was the next
  failure in the ruamel-yaml-clib build).
- tests/install/e2e-assets/source-build-env.ps1: clear the identity variables through the
  env: drive — [Environment]::SetEnvironmentVariable(..., 'Process') on .NET/Unix does not
  reach spawned children, so the stamp child still saw GITHUB_SHA. Red→green under nix pwsh.
- old-updater surface: warm_agent_browser_npx_cache is a permanent def in both facade and
  sibling (the frozen surface names both); its compat pointer is retired, and the shims test's
  __module__ check holds.
- tests re-seamed / de-faked: import guard tests use the probe_root fixture (CI has no
  editable finder), the takeover child tree gets a hermes_constants stub, posix.sh hand-off
  test pins HERMES_HOME (our script honours the ambient one), the two Windows-layout
  PYTHONPATH tests are platforms("windows") (they fake `Lib/site-packages` on Linux; pm's
  site_packages() is host-correct), setup-pin test picks Git bash over System32's WSL stub,
  expose_cli's Windows test asserts the installer-convention convergence (the branch retired
  "windows-installer-owned"), plugin-manifest satisfied-dep fixture uses a core dep (pyyaml is
  gone), housekeeping test yaml imports go through hermes_yaml.
- apps/desktop main.ts: three imports restored in round 4 whose users main removed.

COMPAT_MANIFEST.md

@@ -2960,7 +2960,6 @@ to the public equivalent or the new module. Test monkeypatch seams are likewise
 | `shutil` | import | `shutil` |
 | `signal` | import | `signal` |
 | `timezone` | import | `datetime` |
-| `warm_agent_browser_npx_cache` | moved-lazy | `tools.browser_tool_install` |
 | `windows_hide_flags` | moved-lazy | `hermes_cli._subprocess_compat` |
 
 ### `tools.clarify_gateway`