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_test.go

@@ -153,7 +153,7 @@ func legacyQwenGroupForTest(
 		"matcher": "*",
 		"hooks": []any{map[string]any{
 			"type":    "command",
-			"command": buildQwenCommand(nodePath, scriptPath),
+			"command": buildShellCommand(nodePath, scriptPath),
 			"shell":   qwenExpectedShell(),
 			"timeout": qwenHookTimeout,
 		}},