Passing via `stdin` breaks `pi`

[patrick-kidger]

❯ echo hi | pi --no-tools
^[[?0u^[[6;32;16t
 pi v0.45.7
 escape to interrupt
 ctrl+c to clear
 ctrl+c twice to exit
 ctrl+d to exit (empty)
 ctrl+z to suspend
 ctrl+k to delete to end
 shift+tab to cycle thinking
 ctrl+p/shift+ctrl+p to cycle models
 ctrl+l to select model
 ctrl+o to expand tools
 ctrl+t to toggle thinking
 ctrl+g for external editor
 / for commands
 ! to run bash
 !! to run bash (no context)
 alt+enter to queue follow-up
 alt+up to edit all queued messages
 ctrl+v to paste image
 drop files to attach

Loaded skills:
  /Users/patrickkidger/.claude/skills/coding-python/SKILL.md


────────────────────────────────────────────────────────────────────────────────────────────────
hi

────────────────────────────────────────────────────────────────────────────────────────────────
~/projects/tinyio (detached)
0.0%/200k (auto)                                               claude-opus-4-5-20251101 • medium
Now I type in jkl. Now I will hint Enter:
Now I have hit Enter.
Nothing is being executed?!?

Note the escape sequence at the top, and the result of me typing at the bottom.

AFAICT using stdin isn't documented in any way so perhaps this is just UB rather than a bug.

macOS 26.2 pi 0.45.7