fix(ui): add trim validation for composite tier model fields

- Use z.string().trim().min(1) to reject whitespace-only models
- Apply to all 3 tiers (opus, sonnet, haiku) in both dialogs

ui/src/components/cliproxy/cliproxy-dialog.tsx

@@ -37,17 +37,17 @@ const compositeSchema = z.object({
   tiers: z.object({
     opus: z.object({
       provider: z.enum(CLIPROXY_PROVIDERS, { message: 'Provider is required' }),
-      model: z.string().min(1, 'Model is required'),
+      model: z.string().trim().min(1, 'Model is required'),
       account: z.string().optional(),
     }),
     sonnet: z.object({
       provider: z.enum(CLIPROXY_PROVIDERS, { message: 'Provider is required' }),
-      model: z.string().min(1, 'Model is required'),
+      model: z.string().trim().min(1, 'Model is required'),
       account: z.string().optional(),
     }),
     haiku: z.object({
       provider: z.enum(CLIPROXY_PROVIDERS, { message: 'Provider is required' }),
-      model: z.string().min(1, 'Model is required'),
+      model: z.string().trim().min(1, 'Model is required'),
       account: z.string().optional(),
     }),
   }),

ui/src/components/cliproxy/cliproxy-edit-dialog.tsx

@@ -27,17 +27,17 @@ const compositeSchema = z.object({
   tiers: z.object({
     opus: z.object({
       provider: z.enum(CLIPROXY_PROVIDERS, { message: 'Provider is required' }),
-      model: z.string().min(1, 'Model is required'),
+      model: z.string().trim().min(1, 'Model is required'),
       account: z.string().optional(),
     }),
     sonnet: z.object({
       provider: z.enum(CLIPROXY_PROVIDERS, { message: 'Provider is required' }),
-      model: z.string().min(1, 'Model is required'),
+      model: z.string().trim().min(1, 'Model is required'),
       account: z.string().optional(),
     }),
     haiku: z.object({
       provider: z.enum(CLIPROXY_PROVIDERS, { message: 'Provider is required' }),
-      model: z.string().min(1, 'Model is required'),
+      model: z.string().trim().min(1, 'Model is required'),
       account: z.string().optional(),
     }),
   }),