- Added PTY flags to ShellRunOptions and ShellExecuteOptions and defaulted pty to false when unset.
- Routed PTY-enabled shell runs to a dedicated PTY runner and executed commands via `sh -lc` in a PTY.
- Handled PTY output with a dedicated thread, Chunk/Done events, child PGID cancellation, and drain-timeout cleanup.
- Added Unix-only PTY assertions and non-Windows native coverage for `executeShell` with `pty: true` and `/dev/` output checks.
- Added `portable-pty = "0.9"` (and lockfile update) to enable PTY execution in pi-shell.
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