Fix auto-update by removing stale npm lock file

The auto-update feature was failing to install new versions because npm's
.package-lock.json file in the cache directory was pinning the old version.
This fix removes the lock file before running npm install to force fresh
package resolution.

Author: Tarquinen

lib/version-checker.ts

@@ -55,10 +55,23 @@ export function isOutdated(local: string, remote: string): boolean {
 export async function performUpdate(targetVersion: string, logger?: { info: (component: string, message: string, data?: any) => void }): Promise<boolean> {
     // OpenCode installs packages to ~/.cache/opencode/node_modules/
     const cacheDir = join(homedir(), '.cache', 'opencode')
+    const packageDir = join(cacheDir, 'node_modules', '@tarquinen', 'opencode-dcp')
     const packageSpec = `${PACKAGE_NAME}@${targetVersion}`
 
     logger?.info("version", "Starting auto-update", { targetVersion, cacheDir })
 
+    try {
+        const { rmSync, existsSync } = await import('fs')
+        const lockFile = join(cacheDir, 'node_modules', '.package-lock.json')
+        if (existsSync(lockFile)) {
+            // Remove the lock file to force npm to re-resolve the package
+            rmSync(lockFile, { force: true })
+            logger?.info("version", "Removed package-lock.json to force fresh resolution")
+        }
+    } catch (err) {
+        logger?.info("version", "Could not remove lock file", { error: (err as Error).message })
+    }
+
     return new Promise((resolve) => {
         let resolved = false