refactor: wave 2 - split atlas, auto-update-checker, session-recovery, todo-enforcer, background-task hooks

- Extract atlas/ into 15 focused modules (hook, event handler, tool policies, types, etc.)
- Split auto-update-checker into checker/ and hook/ subdirectories with single-purpose files
- Decompose session-recovery into separate recovery strategy files per error type
- Extract todo-continuation-enforcer from monolith to directory with dedicated modules
- Split background-task/tools.ts into individual tool creator files
- Extract command-executor, tmux-utils into focused sub-modules
- Split config/schema.ts into domain-specific schema files
- Decompose cli/config-manager.ts into focused modules
- Rollback skill-mcp-manager, model-availability, index.ts splits that broke tests
- Fix all import path depths for moved files (../../ -> ../../../)
- Add explicit type annotations to resolve TS7006 implicit any errors

Typecheck: 0 errors
Tests: 2359 pass, 5 fail (all pre-existing)

src/config/schema/agent-overrides.ts

@@ -0,0 +1,60 @@
+import { z } from "zod"
+import { AgentPermissionSchema } from "./internal/permission"
+
+export const AgentOverrideConfigSchema = z.object({
+  /** @deprecated Use `category` instead. Model is inherited from category defaults. */
+  model: z.string().optional(),
+  variant: z.string().optional(),
+  /** Category name to inherit model and other settings from CategoryConfig */
+  category: z.string().optional(),
+  /** Skill names to inject into agent prompt */
+  skills: z.array(z.string()).optional(),
+  temperature: z.number().min(0).max(2).optional(),
+  top_p: z.number().min(0).max(1).optional(),
+  prompt: z.string().optional(),
+  prompt_append: z.string().optional(),
+  tools: z.record(z.string(), z.boolean()).optional(),
+  disable: z.boolean().optional(),
+  description: z.string().optional(),
+  mode: z.enum(["subagent", "primary", "all"]).optional(),
+  color: z
+    .string()
+    .regex(/^#[0-9A-Fa-f]{6}$/)
+    .optional(),
+  permission: AgentPermissionSchema.optional(),
+  /** Maximum tokens for response. Passed directly to OpenCode SDK. */
+  maxTokens: z.number().optional(),
+  /** Extended thinking configuration (Anthropic). Overrides category and default settings. */
+  thinking: z
+    .object({
+      type: z.enum(["enabled", "disabled"]),
+      budgetTokens: z.number().optional(),
+    })
+    .optional(),
+  /** Reasoning effort level (OpenAI). Overrides category and default settings. */
+  reasoningEffort: z.enum(["low", "medium", "high", "xhigh"]).optional(),
+  /** Text verbosity level. */
+  textVerbosity: z.enum(["low", "medium", "high"]).optional(),
+  /** Provider-specific options. Passed directly to OpenCode SDK. */
+  providerOptions: z.record(z.string(), z.unknown()).optional(),
+})
+
+export const AgentOverridesSchema = z.object({
+  build: AgentOverrideConfigSchema.optional(),
+  plan: AgentOverrideConfigSchema.optional(),
+  sisyphus: AgentOverrideConfigSchema.optional(),
+  hephaestus: AgentOverrideConfigSchema.optional(),
+  "sisyphus-junior": AgentOverrideConfigSchema.optional(),
+  "OpenCode-Builder": AgentOverrideConfigSchema.optional(),
+  prometheus: AgentOverrideConfigSchema.optional(),
+  metis: AgentOverrideConfigSchema.optional(),
+  momus: AgentOverrideConfigSchema.optional(),
+  oracle: AgentOverrideConfigSchema.optional(),
+  librarian: AgentOverrideConfigSchema.optional(),
+  explore: AgentOverrideConfigSchema.optional(),
+  "multimodal-looker": AgentOverrideConfigSchema.optional(),
+  atlas: AgentOverrideConfigSchema.optional(),
+})
+
+export type AgentOverrideConfig = z.infer<typeof AgentOverrideConfigSchema>
+export type AgentOverrides = z.infer<typeof AgentOverridesSchema>