Attach shell process listeners before handling already-aborted tool signals so canceled runs always settle, and decode shell output as UTF-8 to preserve multibyte characters across chunk boundaries. Also lazy-load shell-specific parsers and hoist command sets so parsing work stays focused on the active shell.
Move shell tool ID checks behind shared helpers so runtime code and tests stop duplicating bash, pwsh, and powershell branches. This keeps shell-specific behavior aligned across consumers and makes follow-on shell changes less error-prone.
