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/categories.ts

@@ -0,0 +1,40 @@
+import { z } from "zod"
+
+export const CategoryConfigSchema = z.object({
+  /** Human-readable description of the category's purpose. Shown in task prompt. */
+  description: z.string().optional(),
+  model: z.string().optional(),
+  variant: z.string().optional(),
+  temperature: z.number().min(0).max(2).optional(),
+  top_p: z.number().min(0).max(1).optional(),
+  maxTokens: z.number().optional(),
+  thinking: z
+    .object({
+      type: z.enum(["enabled", "disabled"]),
+      budgetTokens: z.number().optional(),
+    })
+    .optional(),
+  reasoningEffort: z.enum(["low", "medium", "high", "xhigh"]).optional(),
+  textVerbosity: z.enum(["low", "medium", "high"]).optional(),
+  tools: z.record(z.string(), z.boolean()).optional(),
+  prompt_append: z.string().optional(),
+  /** Mark agent as unstable - forces background mode for monitoring. Auto-enabled for gemini/minimax models. */
+  is_unstable_agent: z.boolean().optional(),
+})
+
+export const BuiltinCategoryNameSchema = z.enum([
+  "visual-engineering",
+  "ultrabrain",
+  "deep",
+  "artistry",
+  "quick",
+  "unspecified-low",
+  "unspecified-high",
+  "writing",
+])
+
+export const CategoriesConfigSchema = z.record(z.string(), CategoryConfigSchema)
+
+export type CategoryConfig = z.infer<typeof CategoryConfigSchema>
+export type CategoriesConfig = z.infer<typeof CategoriesConfigSchema>
+export type BuiltinCategoryName = z.infer<typeof BuiltinCategoryNameSchema>