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/hooks/auto-update-checker/checker/cached-version.ts

@@ -0,0 +1,45 @@
+import * as fs from "node:fs"
+import * as path from "node:path"
+import { fileURLToPath } from "node:url"
+import { log } from "../../../shared/logger"
+import type { PackageJson } from "../types"
+import { INSTALLED_PACKAGE_JSON } from "../constants"
+import { findPackageJsonUp } from "./package-json-locator"
+
+export function getCachedVersion(): string | null {
+  try {
+    if (fs.existsSync(INSTALLED_PACKAGE_JSON)) {
+      const content = fs.readFileSync(INSTALLED_PACKAGE_JSON, "utf-8")
+      const pkg = JSON.parse(content) as PackageJson
+      if (pkg.version) return pkg.version
+    }
+  } catch {
+    // ignore
+  }
+
+  try {
+    const currentDir = path.dirname(fileURLToPath(import.meta.url))
+    const pkgPath = findPackageJsonUp(currentDir)
+    if (pkgPath) {
+      const content = fs.readFileSync(pkgPath, "utf-8")
+      const pkg = JSON.parse(content) as PackageJson
+      if (pkg.version) return pkg.version
+    }
+  } catch (err) {
+    log("[auto-update-checker] Failed to resolve version from current directory:", err)
+  }
+
+  try {
+    const execDir = path.dirname(fs.realpathSync(process.execPath))
+    const pkgPath = findPackageJsonUp(execDir)
+    if (pkgPath) {
+      const content = fs.readFileSync(pkgPath, "utf-8")
+      const pkg = JSON.parse(content) as PackageJson
+      if (pkg.version) return pkg.version
+    }
+  } catch (err) {
+    log("[auto-update-checker] Failed to resolve version from execPath:", err)
+  }
+
+  return null
+}