feat(04-01): register Athena in builtin agent resolution maps

- add Athena factory and prompt metadata to builtin agent sources

- define Athena fallback chain in AGENT_MODEL_REQUIREMENTS for primary resolution

src/agents/builtin-agents.ts

@@ -12,6 +12,7 @@ import { createMetisAgent, metisPromptMetadata } from "./metis"
 import { createAtlasAgent, atlasPromptMetadata } from "./atlas"
 import { createMomusAgent, momusPromptMetadata } from "./momus"
 import { createHephaestusAgent } from "./hephaestus"
+import { createAthenaAgent, ATHENA_PROMPT_METADATA } from "./athena/agent"
 import type { AvailableCategory } from "./dynamic-agent-prompt-builder"
 import {
   fetchAvailableModels,
@@ -38,6 +39,7 @@ const agentSources: Partial<Record<BuiltinAgentName, AgentSource>> = {
   "multimodal-looker": createMultimodalLookerAgent,
   metis: createMetisAgent,
   momus: createMomusAgent,
+  athena: createAthenaAgent,
   // Note: Atlas is handled specially in createBuiltinAgents()
   // because it needs OrchestratorContext, not just a model string
   atlas: createAtlasAgent as AgentFactory,
@@ -54,6 +56,7 @@ const agentMetadata: Partial<Record<BuiltinAgentName, AgentPromptMetadata>> = {
   "multimodal-looker": MULTIMODAL_LOOKER_PROMPT_METADATA,
   metis: metisPromptMetadata,
   momus: momusPromptMetadata,
+  athena: ATHENA_PROMPT_METADATA,
   atlas: atlasPromptMetadata,
 }
 

src/shared/model-requirements.ts

@@ -89,6 +89,17 @@ export const AGENT_MODEL_REQUIREMENTS: Record<string, ModelRequirement> = {
       { providers: ["openai", "github-copilot", "opencode"], model: "gpt-5.2" },
     ],
   },
+  athena: {
+    fallbackChain: [
+      { providers: ["anthropic", "github-copilot", "opencode"], model: "claude-opus-4-6", variant: "max" },
+      { providers: ["kimi-for-coding"], model: "k2p5" },
+      { providers: ["opencode"], model: "kimi-k2.5-free" },
+      { providers: ["zai-coding-plan"], model: "glm-4.7" },
+      { providers: ["opencode"], model: "glm-4.7-free" },
+      { providers: ["openai", "github-copilot", "opencode"], model: "gpt-5.2", variant: "high" },
+      { providers: ["google", "github-copilot", "opencode"], model: "gemini-3-pro", variant: "high" },
+    ],
+  },
 }
 
 export const CATEGORY_MODEL_REQUIREMENTS: Record<string, ModelRequirement> = {