fix(commands): harden model alias parsing

docs/tools/slash-commands.md

@@ -42,7 +42,7 @@ Text + native (when enabled):
 - `/verbose on|off` (alias: `/v`)
 - `/reasoning on|off|stream` (alias: `/reason`; `stream` = Telegram draft only)
 - `/elevated on|off` (alias: `/elev`)
-- `/model <name>`
+- `/model <name>` (or `/<alias>` from `agent.models.*.alias`)
 - `/queue <mode>` (plus options like `debounce:2s cap:25 drop:summarize`)
 
 Text-only: