feat(workflows): branch event waits by outcome

[vladbisceanu]

What changed

• model WAIT_FOR_EVENT transitions with explicit EVENT and TIMEOUT outcomes
• migrate existing linear waits without breaking legacy explicit timeout fallbacks
• route both outcomes through the same execution path and persist resumed event data in execution context
• expose named routes in the builder, workflow validation, visualizer, API docs, and workflow docs

Why

A wait currently cannot send event arrival and timeout down different paths, and resumed event data is not available to downstream conditions, templates, or webhooks.

Verification

• 96 focused workflow tests on current next
• API build
• web production build
• focused API and web lint
• fresh PostgreSQL migration deploy
• legacy linear and explicit-timeout migration proof
• final local risk review: no findings

Fork integration: vladbisceanu#6. Evaluation tracking: vladbisceanu/setup-works#137.