fix(installer): add upgrade path safety checks

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

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

src/cli/config-manager/detect-current-config.ts

@@ -4,6 +4,7 @@ import type { DetectedConfig } from "../types"
 import { getOmoConfigPath } from "./config-context"
 import { detectConfigFormat } from "./opencode-config-format"
 import { parseOpenCodeConfigFileWithError } from "./parse-opencode-config-file"
+import { extractVersionFromPluginEntry } from "./version-compatibility"
 
 function detectProvidersFromOmoConfig(): {
   hasOpenAI: boolean
@@ -60,9 +61,14 @@ function isOurPlugin(plugin: string): boolean {
          plugin === LEGACY_PLUGIN_NAME || plugin.startsWith(`${LEGACY_PLUGIN_NAME}@`)
 }
 
+function findOurPluginEntry(plugins: string[]): string | null {
+  return plugins.find(isOurPlugin) ?? null
+}
+
 export function detectCurrentConfig(): DetectedConfig {
   const result: DetectedConfig = {
     isInstalled: false,
+    installedVersion: null,
     hasClaude: true,
     isMax20: true,
     hasOpenAI: true,
@@ -86,7 +92,12 @@ export function detectCurrentConfig(): DetectedConfig {
 
   const openCodeConfig = parseResult.config
   const plugins = openCodeConfig.plugin ?? []
-  result.isInstalled = plugins.some(isOurPlugin)
+  const ourPluginEntry = findOurPluginEntry(plugins)
+  result.isInstalled = !!ourPluginEntry
+
+  if (ourPluginEntry) {
+    result.installedVersion = extractVersionFromPluginEntry(ourPluginEntry)
+  }
 
   if (!result.isInstalled) {
     return result