CLI: dblab branch list silently creates a branch named "list"

Found (again) during 4.2 pre-release testing on master @ afcba6c1 (2026-09-08); the same trap bit a customer earlier this year (a stray list branch created by an operator).

dblab branch lists branches; dblab branch <NAME> creates one. Typing the natural dblab branch list therefore creates and switches to a branch named list:

$ dblab branch list
Switched to new branch 'list'
$ dblab branch
  dev1
* list
  main

No confirmation, and the help text (dblab branch [command options] BRANCH_NAME) does not warn. Suggestion: reserve list (and ls) as a subcommand alias for listing, or refuse branch names that collide with common verbs (list, create, delete, switch) unless --name is given.