fix(picker): correct crash-isolation and DPI claims, wire the built-worker guard, and tidy round-four nits

The round-four review's v6 pass found three factual gaps and the v5 pass two
nits. Correct them before merge:

- The in-process note claimed a koffi signature mistake is 'contained to
  the worker thread' — worker_threads share the process, so a native access
  violation takes down the whole Node process with no PowerShell fallback.
  State the real blast radius and record the deferred pkg-VFS worker-spawn
  arm in Consequences (both languages, pairing re-recorded).
- The 2026-07-27 picker note claimed unconditional 'per-monitor-v2 DPI';
  PMv2-less hosts (Server 2016 / Win10 1607) cascade to per-monitor or
  system-aware. Say 'the best thread DPI awareness the host accepts'
  (both languages, pairing re-recorded).
- built-worker.e2e.ts was not in any keyless gate (vitest.e2e config is
  not part of the default unit run and builtBinSmokeGate's explicit list
  missed it), so lib/worker.cjs load regressions passed keyless CI. Add it
  to builtBinSmokeGate alongside the workflow-workerthread sibling.
- Remove the dead trailing 'void bindings' in win32-dialog-logic.spec.ts
  and give native-picker.spec.ts the sibling module header it lacked.

scripts/run-gates.ts

@@ -597,6 +597,7 @@ function builtBinSmokeGate(needs: string[] = ['build']): Gate {
     'apps/cli/tests/built-bin.e2e.ts',
     'packages/examples/cli-demo/tests/built-bin.e2e.ts',
     'packages/examples/acp-demo/tests/built-bin.e2e.ts',
+    'packages/host/directory-picker-native/tests/built-worker.e2e.ts',
     'packages/ui/jsonrpc/tests/built-scope-carrier.e2e.ts',
     // The worker-entry packages' built bundles: the only automated proof
     // that lib/index.js resolves its sibling lib/worker.cjs under plain node