Save As, Save Copy In, Save As Template and Export Selected Tracks as
New Session wrote over any existing file without asking. The Save As
prompt proposes ~/<name>/<name>.scraft, so every new session suggests
~/Untitled/Untitled.scraft, and saving a second new session with the
suggested path replaced the first one.
These commands now refuse to write over an existing file unless
`replace` is true; Save, Save As and Save Copy In may still write the
open session's own file. Scripts, MCP agents and the control channel
can't replace a session by accident. While the path in the prompt names
an existing file, the prompt asks whether to replace it and its OK
button becomes Replace; Enter alone doesn't replace. Saving also
creates the session's folder, so a new session without audio can be
saved to the suggested path. The CLI's --save names its output
explicitly and keeps replacing it, like --bounce.