feat(agents): implement dynamic Sisyphus prompt system with agent metadata

Introduce a new dynamic prompt generation system for Sisyphus orchestrator
that leverages agent metadata for intelligent delegation. This revives the
dynamic-sisyphus-agent-prompt branch with comprehensive refactoring.

Changes:
- Add AgentPromptMetadata, AgentCategory, AgentCost, DelegationTrigger types
- Create sisyphus-prompt-builder with dynamic prompt generation logic
- Add AGENT_PROMPT_METADATA exports to all agent modules (oracle, librarian,
  explore, frontend-ui-ux-engineer, document-writer, multimodal-looker)
- Refactor sisyphus.ts to use buildDynamicSisyphusPrompt()
- Add AvailableAgent type export for type safety

This enables Sisyphus to make intelligent agent selection decisions based on
agent capabilities, costs, and delegation triggers, improving orchestration
efficiency.

🤖 Generated with assistance of OhMyOpenCode
(https://github.com/code-yeongyu/oh-my-opencode)

src/agents/frontend-ui-ux-engineer.ts

@@ -1,7 +1,23 @@
 import type { AgentConfig } from "@opencode-ai/sdk"
+import type { AgentPromptMetadata } from "./types"
 
 const DEFAULT_MODEL = "google/gemini-3-pro-preview"
 
+export const FRONTEND_PROMPT_METADATA: AgentPromptMetadata = {
+  category: "specialist",
+  cost: "CHEAP",
+  promptAlias: "Frontend UI/UX Engineer",
+  triggers: [
+    { domain: "Frontend UI/UX", trigger: "Visual changes only (styling, layout, animation). Pure logic changes in frontend files → handle directly" },
+  ],
+  useWhen: [
+    "Visual/UI/UX changes: Color, spacing, layout, typography, animation, responsive breakpoints, hover states, shadows, borders, icons, images",
+  ],
+  avoidWhen: [
+    "Pure logic: API calls, data fetching, state management, event handlers (non-visual), type definitions, utility functions, business logic",
+  ],
+}
+
 export function createFrontendUiUxEngineerAgent(
   model: string = DEFAULT_MODEL
 ): AgentConfig {