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/version-channel.ts

@@ -0,0 +1,33 @@
+export function isPrereleaseVersion(version: string): boolean {
+  return version.includes("-")
+}
+
+export function isDistTag(version: string): boolean {
+  const startsWithDigit = /^\d/.test(version)
+  return !startsWithDigit
+}
+
+export function isPrereleaseOrDistTag(pinnedVersion: string | null): boolean {
+  if (!pinnedVersion) return false
+  return isPrereleaseVersion(pinnedVersion) || isDistTag(pinnedVersion)
+}
+
+export function extractChannel(version: string | null): string {
+  if (!version) return "latest"
+
+  if (isDistTag(version)) {
+    return version
+  }
+
+  if (isPrereleaseVersion(version)) {
+    const prereleasePart = version.split("-")[1]
+    if (prereleasePart) {
+      const channelMatch = prereleasePart.match(/^(alpha|beta|rc|canary|next)/)
+      if (channelMatch) {
+        return channelMatch[1]
+      }
+    }
+  }
+
+  return "latest"
+}