fix(stapp): raise Loop prompt textarea height from 1 to 68 to satisfy Streamlit minimum (closes #632)

[Kailigithub]

Summary

Raise the Loop prompt textarea minimum height from 1px to 68px to satisfy Streamlit's hard lower bound on st.text_area, which was throwing StreamlitAPIException during sidebar render and collapsing the whole page so the main chat input never appeared.

Root Cause

The exception originates at frontends/stapp.py:145 (was line 124 at the time the issue was filed):

st.text_area("Loop prompt", ..., height=1)

Streamlit's runtime validation rejects height=1 with:

StreamlitAPIException: Invalid height 1px for st.text_area - must be at least 68 pixels.

Sidebar rendering fails → the entire page collapses → the user sees no chat input dialog.

Fix

-    st.text_area("Loop prompt", ..., key="loop_prompt_input", height=1)
+    st.text_area("Loop prompt", ..., key="loop_prompt_input", height=68)

68px is exactly Streamlit's documented minimum. The existing sidebar CSS still overrides the visible height (min-height: 1.6em !important; height: auto !important), so the field continues to grow with content — this change only unblocks Streamlit's API gate.

Scope

• 1 line changed in frontends/stapp.py
• No tests added: the failure is a UI-rendering crash on Streamlit side, not a unit-testable logic path.

Closes #632