Files that use a shared library read its main, never a branch, so a
branch of a library is not isolated in the sense the create dialog
promised. On a shared library the create dialog now says that files
using the library can adopt changes from main only, the chip of a
library branch says the same, and the note beside main reads
"Default branch (read by library consumers)". Other files keep their
copy.
get-file-branch-info returns source-is-shared so a branch knows its
main is a library.
AI-assisted-by: claude-opus-5-5
Signed-off-by: Álvaro Tejero Cantero <alvorithm@teje.ro>
d4f999e6dd