refactor(agents): restructure atlas agent into modular directory with model-based routing

Split monolithic atlas.ts into modular structure: index.ts (routing), default.ts (Claude-optimized), gpt.ts (GPT-optimized), utils.ts (shared utilities). Atlas now routes to appropriate prompt based on model type instead of overriding model settings.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/agents/atlas/utils.ts

@@ -0,0 +1,110 @@
+/**
+ * Atlas Orchestrator - Shared Utilities
+ *
+ * Common functions for building dynamic prompt sections used by both
+ * default (Claude-optimized) and GPT-optimized prompts.
+ */
+
+import type { CategoryConfig } from "../../config/schema"
+import type { AvailableAgent, AvailableSkill } from "../dynamic-agent-prompt-builder"
+import { DEFAULT_CATEGORIES, CATEGORY_DESCRIPTIONS } from "../../tools/delegate-task/constants"
+
+export const getCategoryDescription = (name: string, userCategories?: Record<string, CategoryConfig>) =>
+  userCategories?.[name]?.description ?? CATEGORY_DESCRIPTIONS[name] ?? "General tasks"
+
+export function buildAgentSelectionSection(agents: AvailableAgent[]): string {
+  if (agents.length === 0) {
+    return `##### Option B: Use AGENT directly (for specialized experts)
+
+No agents available.`
+  }
+
+  const rows = agents.map((a) => {
+    const shortDesc = a.description.split(".")[0] || a.description
+    return `| \`${a.name}\` | ${shortDesc} |`
+  })
+
+  return `##### Option B: Use AGENT directly (for specialized experts)
+
+| Agent | Best For |
+|-------|----------|
+${rows.join("\n")}`
+}
+
+export function buildCategorySection(userCategories?: Record<string, CategoryConfig>): string {
+  const allCategories = { ...DEFAULT_CATEGORIES, ...userCategories }
+  const categoryRows = Object.entries(allCategories).map(([name, config]) => {
+    const temp = config.temperature ?? 0.5
+    return `| \`${name}\` | ${temp} | ${getCategoryDescription(name, userCategories)} |`
+  })
+
+  return `##### Option A: Use CATEGORY (for domain-specific work)
+
+Categories spawn \`Sisyphus-Junior-{category}\` with optimized settings:
+
+| Category | Temperature | Best For |
+|----------|-------------|----------|
+${categoryRows.join("\n")}
+
+\`\`\`typescript
+delegate_task(category="[category-name]", load_skills=[...], prompt="...")
+\`\`\``
+}
+
+export function buildSkillsSection(skills: AvailableSkill[]): string {
+  if (skills.length === 0) {
+    return ""
+  }
+
+  const skillRows = skills.map((s) => {
+    const shortDesc = s.description.split(".")[0] || s.description
+    return `| \`${s.name}\` | ${shortDesc} |`
+  })
+
+  return `
+#### 3.2.2: Skill Selection (PREPEND TO PROMPT)
+
+**Skills are specialized instructions that guide subagent behavior. Consider them alongside category selection.**
+
+| Skill | When to Use |
+|-------|-------------|
+${skillRows.join("\n")}
+
+**MANDATORY: Evaluate ALL skills for relevance to your task.**
+
+Read each skill's description and ask: "Does this skill's domain overlap with my task?"
+- If YES: INCLUDE in load_skills=[...]
+- If NO: You MUST justify why in your pre-delegation declaration
+
+**Usage:**
+\`\`\`typescript
+delegate_task(category="[category]", load_skills=["skill-1", "skill-2"], prompt="...")
+\`\`\`
+
+**IMPORTANT:**
+- Skills get prepended to the subagent's prompt, providing domain-specific instructions
+- Subagents are STATELESS - they don't know what skills exist unless you include them
+- Missing a relevant skill = suboptimal output quality`
+}
+
+export function buildDecisionMatrix(agents: AvailableAgent[], userCategories?: Record<string, CategoryConfig>): string {
+  const allCategories = { ...DEFAULT_CATEGORIES, ...userCategories }
+
+  const categoryRows = Object.entries(allCategories).map(([name]) =>
+    `| ${getCategoryDescription(name, userCategories)} | \`category="${name}", load_skills=[...]\` |`
+  )
+
+  const agentRows = agents.map((a) => {
+    const shortDesc = a.description.split(".")[0] || a.description
+    return `| ${shortDesc} | \`agent="${a.name}"\` |`
+  })
+
+  return `##### Decision Matrix
+
+| Task Domain | Use |
+|-------------|-----|
+${categoryRows.join("\n")}
+${agentRows.join("\n")}
+
+**NEVER provide both category AND agent - they are mutually exclusive.**`
+}