a11y: MCP and AI tool lists do not hide commands whose when is false #67

Found while reviewing #66 (part of #64). acture-mcp-server (packages/mcp/src/tools.ts) and acture-ai-vercel (packages/ai-vercel/src/index.ts) call registry.list(opts) without a context, so string when clauses are never evaluated: an unavailable command is listed and fails with when_clause_failed at dispatch. The rule recorded in the acture-palette-design skill is that AI/MCP surfaces should hide unavailable commands. Needs an optional context (or context getter) option on both adapters. Not an a11y item strictly; filed so the skill's table can drop its 'not implemented yet' note.