v1.2.6 — selectable providers for ai nodes
Adds provider selection for do: ai nodes so flow AI can run on a chosen backend instead of racing env keys.
AiNode.provider+PluginConfig.providers/defaultProvider; built-ins openrouter/anthropic/openai.- A selected provider is the single credential path — a stray
OPENROUTER_API_KEYcan't silently win. - Model tiers map to the provider's model IDs;
baseUrltolerates a trailing/v1. - Fully backwards compatible (no provider → env auto-detect).
Fixes the shared-key BYOK bypass (clawnify #828 / PR #41).