fix(effect-acp): elicitation method name and response shape drift from official ACP SDK

[Neon-Wang]

Summary

packages/effect-acp's generated client binds the elicitation request handler to method name session/elicitation (src/_generated/meta.gen.ts), but the official @agent-client-protocol SDK (used by e.g. oh-my-pi 18.x) sends elicitation/create (and elicitation/complete for URL mode). An official-SDK agent that elicits therefore gets -32601 Method not found, and its prompt silently resolves as if the user declined.

Discovered while integrating omp (#9038): omp's approval wrapper calls uiContext.select(...), which over ACP becomes a form elicitation; T3 never saw it, and the tool call auto-denied. #9038 works around this at the adapter boundary via handleUnknownExtRequest.

There is a second drift on the response shape: effect-acp's ElicitationResponse types action as a nested union ({ action: { action: "accept", content? } | { action: "decline" } | { action: "cancel" } }), while the official SDK reads a flat response.action === "accept" string with content beside it. Fixing the method name without flattening the response would still leave official-SDK agents reading "not accepted".

Suggested direction

• Regenerate or hand-patch the client method table to accept elicitation/create (ideally as an alias keeping session/elicitation for older agents), and align ElicitationResponse with the flat official shape.
• The generator script is packages/effect-acp/scripts/generate.ts; worth checking which spec revision it pins against.