[PianoNic]

Summary

• Text Helply writes between tool calls is now part of the reply (normal size and colour) instead of muted rows inside the step list; each run of steps sits between the stretches of text.
• While a reply streams, a run shows its latest three steps with a "+N earlier steps" toggle; steps rise in and fold away. A finished run folds into a one-line summary.
• Reply text and headings use the same 15px typography and spacing as Tessaly; added the fold-away motion utility and translations (de, en, fr, it, rm).

Closes #612