fix(harness-ops,miro): scope $ErrorActionPreference in the Windows repair command #5896

Summary

The Windows PowerShell 5.1 repair line printed by install_command in plugins/harness-ops/skills/inventory/scripts/parser_reader.py and installCommand in plugins/miro/server/src/launcher.ts starts with a top-level $ErrorActionPreference = 'Stop'. Pasted into an interactive session, it leaves the session on Stop after the repair finishes, so later unrelated commands terminate on non-terminating errors.

Fix

Wrap the sequence in a child script block, & { $ErrorActionPreference = 'Stop'; ... }, so the preference is scoped to it; update both tests. Pair with #5880 (miro npm.cmd).

Related

Codex finding past the two-round cap on #5877: #5877 (comment)
#5826, #5880