Global --branch is picked up even when it appears after the subcommand #170

_extract_global_overrides (nsc/cli/app.py:64) scans the whole argv, so a --branch that belongs to a dynamic command (for example a plugin list filter named branch) also switches the whole invocation into that branch. If that branch is merged, the user gets a loud failure when they only wanted to filter. This is the same pre-existing pattern as --profile/--url.

Fix: stop scanning global flags at the first subcommand token, or at least do so for --branch.

Deferred minor from the final review of #167 (NetBox Branching, #166).