feat(hooks): add auto-update-checker for plugin version management

Checks npm registry for latest version on session.created, invalidates
cache and shows toast notification when update is available.

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

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

@@ -0,0 +1,119 @@
+import * as fs from "node:fs"
+import * as path from "node:path"
+import type { NpmDistTags, OpencodeConfig, PackageJson, UpdateCheckResult } from "./types"
+import {
+  PACKAGE_NAME,
+  NPM_REGISTRY_URL,
+  NPM_FETCH_TIMEOUT,
+  INSTALLED_PACKAGE_JSON,
+  USER_OPENCODE_CONFIG,
+} from "./constants"
+import { log } from "../../shared/logger"
+
+export function isLocalDevMode(directory: string): boolean {
+  const projectConfig = path.join(directory, ".opencode", "opencode.json")
+
+  for (const configPath of [projectConfig, USER_OPENCODE_CONFIG]) {
+    try {
+      if (!fs.existsSync(configPath)) continue
+      const content = fs.readFileSync(configPath, "utf-8")
+      const config = JSON.parse(content) as OpencodeConfig
+      const plugins = config.plugin ?? []
+
+      for (const entry of plugins) {
+        if (entry.startsWith("file://") && entry.includes(PACKAGE_NAME)) {
+          return true
+        }
+      }
+    } catch {
+      continue
+    }
+  }
+
+  return false
+}
+
+export function findPluginEntry(directory: string): string | null {
+  const projectConfig = path.join(directory, ".opencode", "opencode.json")
+
+  for (const configPath of [projectConfig, USER_OPENCODE_CONFIG]) {
+    try {
+      if (!fs.existsSync(configPath)) continue
+      const content = fs.readFileSync(configPath, "utf-8")
+      const config = JSON.parse(content) as OpencodeConfig
+      const plugins = config.plugin ?? []
+
+      for (const entry of plugins) {
+        if (entry === PACKAGE_NAME || entry.startsWith(`${PACKAGE_NAME}@`)) {
+          return entry
+        }
+      }
+    } catch {
+      continue
+    }
+  }
+
+  return null
+}
+
+export function getCachedVersion(): string | null {
+  try {
+    if (!fs.existsSync(INSTALLED_PACKAGE_JSON)) return null
+    const content = fs.readFileSync(INSTALLED_PACKAGE_JSON, "utf-8")
+    const pkg = JSON.parse(content) as PackageJson
+    return pkg.version ?? null
+  } catch {
+    return null
+  }
+}
+
+export async function getLatestVersion(): Promise<string | null> {
+  const controller = new AbortController()
+  const timeoutId = setTimeout(() => controller.abort(), NPM_FETCH_TIMEOUT)
+
+  try {
+    const response = await fetch(NPM_REGISTRY_URL, {
+      signal: controller.signal,
+      headers: { Accept: "application/json" },
+    })
+
+    if (!response.ok) return null
+
+    const data = (await response.json()) as NpmDistTags
+    return data.latest ?? null
+  } catch {
+    return null
+  } finally {
+    clearTimeout(timeoutId)
+  }
+}
+
+export async function checkForUpdate(directory: string): Promise<UpdateCheckResult> {
+  if (isLocalDevMode(directory)) {
+    log("[auto-update-checker] Local dev mode detected, skipping update check")
+    return { needsUpdate: false, currentVersion: null, latestVersion: null, isLocalDev: true }
+  }
+
+  const pluginEntry = findPluginEntry(directory)
+  if (!pluginEntry) {
+    log("[auto-update-checker] Plugin not found in config")
+    return { needsUpdate: false, currentVersion: null, latestVersion: null, isLocalDev: false }
+  }
+
+  const currentVersion = getCachedVersion()
+  if (!currentVersion) {
+    log("[auto-update-checker] No cached version found")
+    return { needsUpdate: false, currentVersion: null, latestVersion: null, isLocalDev: false }
+  }
+
+  const latestVersion = await getLatestVersion()
+  if (!latestVersion) {
+    log("[auto-update-checker] Failed to fetch latest version")
+    return { needsUpdate: false, currentVersion, latestVersion: null, isLocalDev: false }
+  }
+
+  const needsUpdate = currentVersion !== latestVersion
+  log(`[auto-update-checker] Current: ${currentVersion}, Latest: ${latestVersion}, NeedsUpdate: ${needsUpdate}`)
+
+  return { needsUpdate, currentVersion, latestVersion, isLocalDev: false }
+}