fix(desktop): show custom (non-curated) model in Settings model pickers

A Radix <Select> renders a blank trigger when its `value` matches no
<SelectItem>. The Settings model pickers built their options solely from
each provider's curated `models` list, so a model added via config that
isn't in that list (e.g. anthropic/claude-opus-4.7 on nous) selected
nothing and showed an empty selector.

Union the active value into the options via a small `withActive` helper,
applied to the main, auxiliary, MoA reference, and MoA aggregator model
selects so the configured model always stays visible and selectable.

apps/desktop/src/app/settings/model-settings.tsx

@@ -78,6 +78,12 @@ const AUX_TASKS: readonly AuxTaskMeta[] = [
 
 const NO_PROVIDERS: readonly ModelOptionProvider[] = [{ name: '—', slug: '', models: [] }]
 
+// Radix <Select> renders a blank trigger when `value` matches no <SelectItem>.
+// A custom model (e.g. one added via config that isn't in the provider's
+// curated list) would vanish — surface the active value so it stays selectable.
+export const withActive = (models: readonly string[], active: string): readonly string[] =>
+  active && !models.includes(active) ? [active, ...models] : models
+
 interface StaleAuxWarningProps {
   applying: boolean
   onReset: () => void
@@ -555,7 +561,7 @@ export function ModelSettings({ onMainModelChanged }: ModelSettingsProps) {
                   <SelectValue placeholder={m.model} />
                 </SelectTrigger>
                 <SelectContent>
-                  {(selectedProviderModels.length ? selectedProviderModels : []).map(model => (
+                  {withActive(selectedProviderModels, selectedModel).map(model => (
                     <SelectItem key={model} value={model}>
                       {model}
                     </SelectItem>
@@ -708,7 +714,7 @@ export function ModelSettings({ onMainModelChanged }: ModelSettingsProps) {
                           <SelectValue placeholder={m.model} />
                         </SelectTrigger>
                         <SelectContent>
-                          {(auxDraftProviderModels.length ? auxDraftProviderModels : []).map(model => (
+                          {withActive(auxDraftProviderModels, auxDraft.model).map(model => (
                             <SelectItem key={model} value={model}>
                               {model}
                             </SelectItem>
@@ -880,7 +886,7 @@ export function ModelSettings({ onMainModelChanged }: ModelSettingsProps) {
                         <SelectValue placeholder={m.model} />
                       </SelectTrigger>
                       <SelectContent>
-                        {modelsForProvider(slot.provider).map(model => (
+                        {withActive(modelsForProvider(slot.provider), slot.model).map(model => (
                           <SelectItem key={model} value={model}>
                             {model}
                           </SelectItem>
@@ -957,7 +963,10 @@ export function ModelSettings({ onMainModelChanged }: ModelSettingsProps) {
                       <SelectValue placeholder={m.model} />
                     </SelectTrigger>
                     <SelectContent>
-                      {modelsForProvider(currentMoaPreset.aggregator.provider).map(model => (
+                      {withActive(
+                        modelsForProvider(currentMoaPreset.aggregator.provider),
+                        currentMoaPreset.aggregator.model
+                      ).map(model => (
                         <SelectItem key={model} value={model}>
                           {model}
                         </SelectItem>

apps/desktop/src/app/settings/with-active.test.ts

@@ -0,0 +1,34 @@
+import { describe, expect, it } from 'vitest'
+
+import { withActive } from './model-settings'
+
+// A Radix <Select> shows a blank trigger when its `value` matches no
+// <SelectItem>. `withActive` guarantees the controlled value is always
+// representable so a config-only / custom model never renders blank.
+describe('withActive', () => {
+  const curated = ['hermes-4', 'hermes-4-mini']
+
+  it('prepends a custom model missing from the curated list', () => {
+    expect(withActive(curated, 'anthropic/claude-opus-4.7')).toEqual([
+      'anthropic/claude-opus-4.7',
+      ...curated
+    ])
+  })
+
+  it('leaves the list untouched when the active model is already curated', () => {
+    expect(withActive(curated, 'hermes-4')).toEqual(curated)
+  })
+
+  it('does not inject an empty active value', () => {
+    expect(withActive(curated, '')).toEqual(curated)
+  })
+
+  it('surfaces the active model even when the curated list is empty', () => {
+    expect(withActive([], 'anthropic/claude-opus-4.7')).toEqual(['anthropic/claude-opus-4.7'])
+  })
+
+  it('keeps the active model selectable as the invariant', () => {
+    const out = withActive(curated, 'custom/model')
+    expect(out).toContain('custom/model')
+  })
+})