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/hook/update-toasts.ts

@@ -0,0 +1,34 @@
+import type { PluginInput } from "@opencode-ai/plugin"
+import { log } from "../../../shared/logger"
+
+export async function showUpdateAvailableToast(
+  ctx: PluginInput,
+  latestVersion: string,
+  getToastMessage: (isUpdate: boolean, latestVersion?: string) => string
+): Promise<void> {
+  await ctx.client.tui
+    .showToast({
+      body: {
+        title: `OhMyOpenCode ${latestVersion}`,
+        message: getToastMessage(true, latestVersion),
+        variant: "info" as const,
+        duration: 8000,
+      },
+    })
+    .catch(() => {})
+  log(`[auto-update-checker] Update available toast shown: v${latestVersion}`)
+}
+
+export async function showAutoUpdatedToast(ctx: PluginInput, oldVersion: string, newVersion: string): Promise<void> {
+  await ctx.client.tui
+    .showToast({
+      body: {
+        title: "OhMyOpenCode Updated!",
+        message: `v${oldVersion} → v${newVersion}\nRestart OpenCode to apply.`,
+        variant: "success" as const,
+        duration: 8000,
+      },
+    })
+    .catch(() => {})
+  log(`[auto-update-checker] Auto-updated toast shown: v${oldVersion} → v${newVersion}`)
+}