Branch failure during --saved filter loading ignores -o json #173

_resolve_saved_filters (nsc/cli/registration.py:127, called at line ~204) runs outside the handler's try block. A BranchError raised there (for example while loading native SavedFilters while in a merged branch) reaches main()'s catch-all. That still emits a branch envelope, but always in TABLE format, ignoring -o json, which breaks the machine-readable error contract for agents.

Fix: catch BranchError/HTTP errors around saved-filter resolution and emit with ctx.output_format.

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