Add a `mode: 'multi'` variant to CONDITION steps that allows matching a
field against multiple values, each routing to its own named branch.
Branches are evaluated in order; first match wins. A `default` branch
catches unmatched contacts.
- Schema: z.union for legacy binary + multi-branch condition configs
- Backend: executeCondition handles multi-branch evaluation with stable
branch IDs, falls back to default when no branch matches
- Builder: Dynamic branch rendering with per-branch colors/labels,
dagre layout spreads branches horizontally
- Config UI: Mode toggle (Simple If/Else vs Multi-branch Switch),
dynamic branch list with add/remove
- Tests: 8 new multi-branch tests covering matching, ordering, default
fallback, mixed operators, and transition routing
- Full backward compatibility: all changes gated on config.mode === 'multi'
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
