fix: prevent auto-update from downgrading prerelease/dist-tag versions (#615)

* fix: prevent auto-update from downgrading prerelease/dist-tag versions

The auto-update checker was incorrectly updating pinned prerelease versions
(e.g., 3.0.0-beta.1) and dist-tags (e.g., @beta) to the stable latest version
from npm, effectively downgrading users who opted into beta.

Added isPrereleaseOrDistTag() check that skips auto-update when:
- Version contains '-' (prerelease like 3.0.0-beta.1)
- Version is a dist-tag (non-semver like beta, next, canary)

Fixes #613

* refactor: export version helpers and import in tests

Address review feedback: export isPrereleaseVersion, isDistTag, and
isPrereleaseOrDistTag from index.ts and import them in tests instead
of duplicating the logic.

src/hooks/auto-update-checker/index.ts

@@ -9,6 +9,20 @@ import type { AutoUpdateCheckerOptions } from "./types"
 
 const SISYPHUS_SPINNER = ["·", "•", "●", "○", "◌", "◦", " "]
 
+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 createAutoUpdateCheckerHook(ctx: PluginInput, options: AutoUpdateCheckerOptions = {}) {
   const { showStartupToast = true, isSisyphusEnabled = false, autoUpdate = true } = options
 
@@ -63,7 +77,7 @@ export function createAutoUpdateCheckerHook(ctx: PluginInput, options: AutoUpdat
 }
 
 async function runBackgroundUpdateCheck(
-  ctx: PluginInput, 
+  ctx: PluginInput,
   autoUpdate: boolean,
   getToastMessage: (isUpdate: boolean, latestVersion?: string) => string
 ): Promise<void> {
@@ -100,6 +114,11 @@ async function runBackgroundUpdateCheck(
   }
 
   if (pluginInfo.isPinned) {
+    if (isPrereleaseOrDistTag(pluginInfo.pinnedVersion)) {
+      log(`[auto-update-checker] Skipping auto-update for prerelease/dist-tag: ${pluginInfo.pinnedVersion}`)
+      return
+    }
+
     const updated = updatePinnedVersion(pluginInfo.configPath, pluginInfo.entry, latestVersion)
     if (!updated) {
       await showUpdateAvailableToast(ctx, latestVersion, getToastMessage)
@@ -112,7 +131,7 @@ async function runBackgroundUpdateCheck(
   invalidatePackage(PACKAGE_NAME)
 
   const installSuccess = await runBunInstallSafe()
-  
+
   if (installSuccess) {
     await showAutoUpdatedToast(ctx, currentVersion, latestVersion)
     log(`[auto-update-checker] Update installed: ${currentVersion} → ${latestVersion}`)
@@ -180,7 +199,7 @@ async function showSpinnerToast(ctx: PluginInput, version: string, message: stri
 }
 
 async function showUpdateAvailableToast(
-  ctx: PluginInput, 
+  ctx: PluginInput,
   latestVersion: string,
   getToastMessage: (isUpdate: boolean, latestVersion?: string) => string
 ): Promise<void> {