feat(pwsh): add the pwsh-local executor and the pwsh tool

Windows-native execution foundation: PwshLocalExecutor implements the bash
executor seam over ctx.subprocess (pwsh -NoLogo -NoProfile -NonInteractive
-Command, one argv element, no quoting layer; resolvePwshPath probes
PowerShell 7 / PATH / Windows PowerShell 5.1 as a pure function), and
tool-pwsh is the minimal PowerShell-dialect model-facing tool over ctx.bash
(foreground only, managed DSH_* env, timeout/signal/exit markers, terminal
and generic presenters). Both packages carry full suites (real pwsh,
self-skipping without it) at per-file 100% coverage; vitest's Windows
exclusion narrows from packages/bash/* to the bash-requiring packages so the
pwsh suites run natively on Windows too. The CLI gains the workspace deps
and tsconfig projects without mounting either plugin; the Windows-default
roadmap is recorded as a proposed Agent Note.

apps/cli/package.json

@@ -77,6 +77,7 @@
     "@deepseek-ai/dsh-repeat-tool-guard": "workspace:^",
     "@deepseek-ai/dsh-pty": "workspace:^",
     "@deepseek-ai/dsh-pty-local": "workspace:^",
+    "@deepseek-ai/dsh-pwsh-local": "workspace:^",
     "@deepseek-ai/dsh-sandbox-local": "workspace:^",
     "@deepseek-ai/dsh-sandbox-policy": "workspace:^",
     "@deepseek-ai/dsh-scope": "workspace:^",
@@ -120,6 +121,7 @@
     "@deepseek-ai/dsh-tool-skill": "workspace:^",
     "@deepseek-ai/dsh-tool-str-replace-editor": "workspace:^",
     "@deepseek-ai/dsh-tool-subagent": "workspace:^",
+    "@deepseek-ai/dsh-tool-pwsh": "workspace:^",
     "@deepseek-ai/dsh-tool-tasks": "workspace:^",
     "@deepseek-ai/dsh-tool-todo": "workspace:^",
     "@deepseek-ai/dsh-tool-web": "workspace:^",