Fix: Remove schema default from analysis_mode, rely on form defaultValues

- Removed .default('deep') from Zod schema to fix type inference
- The field is now purely required with no optional inference
- The default value is provided by useForm's defaultValues
- This cleanly separates schema validation from form defaults

.claude/worktrees/dazzling-leakey

@@ -1 +1 @@
-Subproject commit a02ffd63fe1f8cdee302c03b0d7dca86c9631c15
+Subproject commit 26f91ef0e47bc70526accb11dc43d2c20ea07a55

frontend/components/analysis/AnalysisForm.tsx

@@ -52,7 +52,7 @@ const formSchema = z.object({
     .regex(/^\d{4}-\d{2}-\d{2}$/, "日期格式必須為 YYYY-MM-DD"),
   analysts: z.array(z.string()).min(1, "請至少選擇一位分析師"),
   research_depth: z.number().int().min(1).max(5),
-  analysis_mode: z.enum(["fast", "deep"]).default("deep"),
+  analysis_mode: z.enum(["fast", "deep"]),
   quick_think_llm: z.string().min(1, "請選擇快速思維模型"),
   deep_think_llm: z.string().min(1, "請選擇深層思維模型"),
   embedding_model: z.string().min(1, "請選擇嵌入式模型"),