fix: slug-generator uses configured default model instead of hardcoded Opus

Resolves #4315. The slug-generator embedded run was hardcoded to use
DEFAULT_MODEL (claude-opus-4-5) regardless of the user's configured
agents.defaults.model.primary. This caused unexpected Opus charges on
every /new command.

Now uses resolveDefaultModelForAgent() to honor the user's configured
default model, falling back to DEFAULT_MODEL only when no config exists.

src/hooks/llm-slug-generator.ts

@@ -12,6 +12,7 @@ import {
   resolveAgentWorkspaceDir,
   resolveAgentDir,
 } from "../agents/agent-scope.js";
+import { resolveDefaultModelForAgent } from "../agents/model-selection.js";
 
 /**
  * Generate a short 1-2 word filename slug from session content using LLM
@@ -38,6 +39,11 @@ ${params.sessionContent.slice(0, 2000)}
 
 Reply with ONLY the slug, nothing else. Examples: "vendor-pitch", "api-design", "bug-fix"`;
 
+    // Resolve user's configured default model instead of hardcoded Opus
+    const { provider, model } = resolveDefaultModelForAgent({
+      cfg: params.cfg,
+    });
+
     const result = await runEmbeddedPiAgent({
       sessionId: `slug-generator-${Date.now()}`,
       sessionKey: "temp:slug-generator",
@@ -46,6 +52,8 @@ Reply with ONLY the slug, nothing else. Examples: "vendor-pitch", "api-design",
       agentDir,
       config: params.cfg,
       prompt,
+      provider,
+      model,
       timeoutMs: 15_000, // 15 second timeout
       runId: `slug-gen-${Date.now()}`,
     });
@@ -75,7 +83,10 @@ Reply with ONLY the slug, nothing else. Examples: "vendor-pitch", "api-design",
     // Clean up temporary session file
     if (tempSessionFile) {
       try {
-        await fs.rm(path.dirname(tempSessionFile), { recursive: true, force: true });
+        await fs.rm(path.dirname(tempSessionFile), {
+          recursive: true,
+          force: true,
+        });
       } catch {
         // Ignore cleanup errors
       }