fix(auto-update): pipe bun install output and restore other-deps preservation test

background-update-check.ts was using runBunInstall() which defaults to outputMode:"inherit", leaking bun install stdout/stderr into the background session. Reverted to runBunInstallWithDetails({ outputMode: "pipe" }) and explicitly logs result.error on failure.

Restores the accidentally deleted test case asserting that sibling dependencies (e.g. other:"1.0.0") are preserved in package.json after a plugin version sync.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/auto-update-checker/hook/background-update-check.ts

@@ -1,5 +1,5 @@
 import type { PluginInput } from "@opencode-ai/plugin"
-import { runBunInstall } from "../../../cli/config-manager"
+import { runBunInstallWithDetails } from "../../../cli/config-manager"
 import { log } from "../../../shared/logger"
 import { invalidatePackage } from "../cache"
 import { PACKAGE_NAME } from "../constants"
@@ -13,7 +13,11 @@ function getPinnedVersionToastMessage(latestVersion: string): string {
 
 async function runBunInstallSafe(): Promise<boolean> {
   try {
-    return await runBunInstall()
+    const result = await runBunInstallWithDetails({ outputMode: "pipe" })
+    if (!result.success && result.error) {
+      log("[auto-update-checker] bun install error:", result.error)
+    }
+    return result.success
   } catch (err) {
     const errorMessage = err instanceof Error ? err.message : String(err)
     log("[auto-update-checker] bun install error:", errorMessage)