Add a separate e2e Go module that validates the shell integrations
against real shells instead of only asserting generated script text:
- layer 1: generate the init script per shell and feature-config
overlay (base, transient, rprompt, tooltips, full) and validate it
with the shell's own parser
- layer 2: boot each shell interactively in a pty (ConPTY on Windows,
creack/pty elsewhere) with a vt10x screen emulator, assert the
prompt renders and the session exits cleanly
- layer 3: feature scenarios asserting exit-code propagation,
transient prompt replacement, and rprompt right-alignment
Covers bash, zsh, fish, pwsh, and nu; tests skip cleanly when a shell
binary is absent or the platform cannot drive it faithfully. The
harness answers PSReadLine's DSR cursor queries on Unix ptys and
isolates sessions from the host's cache and nu vendor autoloads.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Entire-Checkpoint: 8a75c4edb40b
