Fix non-TTY interactive chat launch handling

[pandego]

Summary

• require a real TTY before starting interactive hermes chat
• skip the post-setup hermes chat handoff entirely when stdin is non-interactive
• preserve single-query hermes chat -q ... behavior for headless and piped use cases

Issues

• Closes [Setup]: OSError: [Errno 22] Invalid argument:[prompt_toolkit crash] #5884
• Closes [Bug]: after install it, startup failed #6393

Root cause

Interactive chat startup had a TTY requirement in the codebase, but the hermes chat path was not enforcing it before handing off to the prompt_toolkit TUI. Separately, setup could still offer and exec into chat after configuration even when stdin was not a TTY. In headless environments that led to invalid interactive launches and downstream stdin attachment crashes.

Fix

This keeps the change narrow and explicit:

• interactive chat now fails fast with the existing TTY guard when no --query was provided
• non-interactive single-query mode still bypasses the TTY requirement
• setup now returns early from the post-setup launch helper when stdin is not interactive, so it neither prompts nor attempts to exec into chat

Validation

• uv run --python 3.11 --extra dev python -m pytest tests/hermes_cli/test_setup_noninteractive.py -n 0
  • passed

[alt-glitch]

Related to #10558, #8842, #15720 (all addressing non-TTY chat launch). See also #8641 (parent issue). Consider consolidating.

[pandego]

closing this to reduce overlap. there are a few open PRs covering the same non-tty chat path