fix(status): include provider prefix in model display

The /status command was showing 'anthropic/claude-sonnet-4-5' even when
using 'google-antigravity/claude-sonnet-4-5' because buildStatusMessage
received only the model name without the provider prefix.

When resolveConfiguredModelRef parsed a model string without a slash,
it fell back to DEFAULT_PROVIDER ('anthropic'), causing the misleading
display.

Fix: Pass the full 'provider/model' string to buildStatusMessage so
the provider is correctly extracted and displayed.

🪿 Investigated and submitted by Keith the Silly Goose

src/auto-reply/reply/commands.ts

@@ -444,7 +444,7 @@ export async function handleCommands(params: {
         ...cfg.agent,
         model: {
           ...cfg.agent?.model,
-          primary: model,
+          primary: `${provider}/${model}`,
         },
         contextTokens,
         thinkingDefault: cfg.agent?.thinkingDefault,