chore(go): audit providers kimi grok qwen letta

Move Kimi, Grok, and Qwen onto managed_runtime.go and shell_command.go;
share the encoded and shell command builders and the quoted Windows
legacy parser with Droid; split managed_changes.go; dedupe Letta's hook
entry filtering and stop swallowing settings read errors.

Claude-Session: https://claude.ai/code/session_01Agoc9bRVE9KL7mmWtey9Vq

cmd/elydora/plugins/qwen_status.go

@@ -0,0 +1,5 @@
+package plugins
+
+func qwenRuntimeFilesExist(contracts []managedRuntimeContract) (bool, error) {
+	return managedRuntimeFilesExist(contracts, qwenAgentKey, "Qwen Code", qwenExpectedScripts)
+}