Model retry alternative strategy plugin

Key features

• Automatic fallback for root and subagents: any agent switches down the chain to the next available provider/model on model failure — no manual model switching.
• Session origin (root / subagent) and the resolved role (the role of the first matching roles.rules entry, otherwise the built-in inherit)
• No patches, no auto-apply stepthere are no dsh-body patch files and no install lifecycle step that applies one.
• Two-block configblock 1 rootChain — the root agent's single fallback chain (empty = root does not fall back)
• block 2 declared roles — roles.list role entities (id/persona/chain/fallback) that roles.rules reference by id (or the built-in inherit)