Sherpa as a host-agnostic agent plugin

[20001LastOrder]

Once the core is decoupled (#514), Sherpa can ship as a plugin for whichever agent the user already runs, Claude Code, Codex, others, supplying explicit workflows, states and guardrails on top of the host's own model and tools.

• Define the host interface once, then bind it per host — Claude Code first, Codex as the second target to prove it generalizes
• Map Sherpa actions onto host-side skills and runnable scripts
• Decide packaging per host: plugin, MCP server, or both
• State the differentiator against a stock agent loop: dynamic workflow, visualization of alternatives, guardrails