chore(go): audit providers claudecode codex cursor gemini

Add managed_runtime.go (paths, config validation, identity, runtime file
changes, status checks) and shell_command.go (quoting, PowerShell
encoding, command parsing) and move the four providers onto them.

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

cmd/elydora/plugins/kiroide_test.go

@@ -331,7 +331,7 @@ func TestKiroIdeStatusRejectsStaleWindowsPowerShellLauncher(t *testing.T) {
 	command := action["command"].(string)
 	action["command"] = strings.Replace(
 		command,
-		codexPowerShellPath(),
+		windowsPowerShellPath(),
 		`C:\StaleWindows\System32\WindowsPowerShell\v1.0\powershell.exe`,
 		1,
 	)