fix(auto-update): sync cache package.json to opencode.json intent

When users switch opencode.json from pinned version to tag (e.g., 3.10.0 -> @latest),
the cache package.json still contains the pinned version. This causes bun install
to reinstall the old version instead of resolving the new tag.

This adds syncCachePackageJsonToIntent() which updates the cache package.json
to match the user's declared intent in opencode.json before running bun install.

Also fixes mock.module in test files to include all exported constants,
preventing module pollution across parallel tests.

src/hooks/auto-update-checker/checker/sync-package-json.ts

@@ -0,0 +1,88 @@
+import * as fs from "node:fs"
+import * as path from "node:path"
+import { CACHE_DIR, PACKAGE_NAME } from "../constants"
+import { log } from "../../../shared/logger"
+import type { PluginEntryInfo } from "./plugin-entry"
+
+interface CachePackageJson {
+  dependencies?: Record<string, string>
+}
+
+/**
+ * Determine the version specifier to use in cache package.json based on opencode.json intent.
+ *
+ * - "oh-my-opencode" (no version) → "latest"
+ * - "oh-my-opencode@latest" → "latest"
+ * - "oh-my-opencode@next" → "next"
+ * - "oh-my-opencode@3.10.0" → "3.10.0" (pinned, use as-is)
+ */
+function getIntentVersion(pluginInfo: PluginEntryInfo): string {
+  if (!pluginInfo.pinnedVersion) {
+    // No version specified in opencode.json, default to latest
+    return "latest"
+  }
+  return pluginInfo.pinnedVersion
+}
+
+/**
+ * Sync the cache package.json to match the opencode.json plugin intent.
+ *
+ * OpenCode pins resolved versions in cache package.json (e.g., "3.11.0" instead of "latest").
+ * This causes issues when users switch from pinned to tag in opencode.json:
+ * - User changes opencode.json from "oh-my-opencode@3.10.0" to "oh-my-opencode@latest"
+ * - Cache package.json still has "3.10.0"
+ * - bun install reinstalls 3.10.0 instead of resolving @latest
+ *
+ * This function updates cache package.json to match the user's intent before bun install.
+ *
+ * @returns true if package.json was updated, false otherwise
+ */
+export function syncCachePackageJsonToIntent(pluginInfo: PluginEntryInfo): boolean {
+  const cachePackageJsonPath = path.join(CACHE_DIR, "package.json")
+
+  if (!fs.existsSync(cachePackageJsonPath)) {
+    log("[auto-update-checker] Cache package.json not found, nothing to sync")
+    return false
+  }
+
+  try {
+    const content = fs.readFileSync(cachePackageJsonPath, "utf-8")
+    const pkgJson = JSON.parse(content) as CachePackageJson
+
+    if (!pkgJson.dependencies?.[PACKAGE_NAME]) {
+      log("[auto-update-checker] Plugin not in cache package.json dependencies, nothing to sync")
+      return false
+    }
+
+    const currentVersion = pkgJson.dependencies[PACKAGE_NAME]
+    const intentVersion = getIntentVersion(pluginInfo)
+
+    if (currentVersion === intentVersion) {
+      log("[auto-update-checker] Cache package.json already matches intent:", intentVersion)
+      return false
+    }
+
+    // Check if this is a meaningful change:
+    // - If intent is a tag (latest, next, beta) and current is semver, we need to update
+    // - If both are semver but different, user explicitly changed versions
+    const intentIsTag = !/^\d+\.\d+\.\d+/.test(intentVersion)
+    const currentIsSemver = /^\d+\.\d+\.\d+/.test(currentVersion)
+
+    if (intentIsTag && currentIsSemver) {
+      log(
+        `[auto-update-checker] Syncing cache package.json: "${currentVersion}" → "${intentVersion}" (opencode.json intent)`
+      )
+    } else {
+      log(
+        `[auto-update-checker] Updating cache package.json: "${currentVersion}" → "${intentVersion}"`
+      )
+    }
+
+    pkgJson.dependencies[PACKAGE_NAME] = intentVersion
+    fs.writeFileSync(cachePackageJsonPath, JSON.stringify(pkgJson, null, 2))
+    return true
+  } catch (err) {
+    log("[auto-update-checker] Failed to sync cache package.json:", err)
+    return false
+  }
+}