🤖 fix: use defaultModel directly instead of wrapper (#626)

Remove unnecessary defaults.ts wrapper that was created in the import
linting changes.

## Changes

- Remove `src/common/utils/model/defaults.ts`
- Update CLI files to import `defaultModel` directly from
`@/common/utils/ai/models`
  - `agentSessionCli.ts`
  - `costs.ts`
  - `send-message.ts`

## Context

The original changes moved shared code to `common/` to fix ESLint
boundary violations. However, the CLI doesn't need a wrapper function -
it can import the `defaultModel` constant directly.

_Generated with `mux`_

Author: kylecarbs

src/cli/debug/agentSessionCli.ts

@@ -24,7 +24,7 @@ import {
   type SendMessageOptions,
   type WorkspaceChatMessage,
 } from "@/common/types/ipc";
-import { getDefaultModel } from "@/common/utils/model/defaults";
+import { defaultModel } from "@/common/utils/ai/models";
 import { ensureProvidersConfig } from "@/common/utils/providers/ensureProvidersConfig";
 import { modeToToolPolicy, PLAN_MODE_INSTRUCTION } from "@/common/utils/ui/modeUtils";
 import {
@@ -183,8 +183,7 @@ async function main(): Promise<void> {
     throw new Error("Message must be provided via --message or stdin");
   }
 
-  const model =
-    values.model && values.model.trim().length > 0 ? values.model.trim() : getDefaultModel();
+  const model = values.model && values.model.trim().length > 0 ? values.model.trim() : defaultModel;
   const timeoutMs = parseTimeout(values.timeout);
   const thinkingLevel = parseThinkingLevel(values["thinking-level"]);
   const initialMode = parseMode(values.mode);

src/cli/debug/costs.ts

@@ -3,7 +3,7 @@ import * as path from "path";
 import { defaultConfig } from "@/node/config";
 import type { MuxMessage } from "@/common/types/message";
 import { calculateTokenStats } from "@/common/utils/tokens/tokenStatsCalculator";
-import { getDefaultModel } from "@/common/utils/model/defaults";
+import { defaultModel } from "@/common/utils/ai/models";
 
 /**
  * Debug command to display cost/token statistics for a workspace
@@ -35,7 +35,7 @@ export async function costsCommand(workspaceId: string) {
 
   // Detect model from first assistant message
   const firstAssistantMessage = messages.find((msg) => msg.role === "assistant");
-  const model = firstAssistantMessage?.metadata?.model ?? getDefaultModel();
+  const model = firstAssistantMessage?.metadata?.model ?? defaultModel;
 
   // Calculate stats using shared logic (now synchronous)
   const stats = await calculateTokenStats(messages, model);

src/cli/debug/send-message.ts

@@ -3,7 +3,7 @@ import * as path from "path";
 import { defaultConfig } from "@/node/config";
 import type { MuxMessage } from "@/common/types/message";
 import type { SendMessageOptions } from "@/common/types/ipc";
-import { getDefaultModel } from "@/common/utils/model/defaults";
+import { defaultModel } from "@/common/utils/ai/models";
 import { getMuxSessionsDir } from "@/common/constants/paths";
 
 /**
@@ -104,7 +104,7 @@ export function sendMessageCommand(
 
   // Prepare options
   const options: SendMessageOptions = {
-    model: getDefaultModel(),
+    model: defaultModel,
   };
 
   if (editMessageId) {