fix(gateway): expose MiMo model variants to OpenCode clients (#1644)

## Summary

- Xiaomi MiMo models (`xiaomi/mimo-v2-pro:free` and
`xiaomi/mimo-v2-omni:free`) were missing `opencode.variants`
configuration, causing OpenCode clients on Kilo Gateway to not properly
recognize or surface these reasoning models.
- Added `isXiaomiModel` to the variant detection in `getModelVariants()`
so MiMo models now expose `instant` (reasoning disabled) and `thinking`
(reasoning enabled) variants, matching the pattern used by other
reasoning models like Moonshot and ZAI.
- Updated the approved test snapshot to reflect the new opencode variant
settings for both MiMo models.

Closes #1641

## Verification

- [x] `pnpm typecheck` — passed, no errors
- [x] Manual review of `getOpenCodeSettings()` flow confirms MiMo models
now return `{ variants: { instant: ..., thinking: ... } }` instead of
`{}`

## Visual Changes

N/A

## Reviewer Notes

- The fix adds `isXiaomiModel(model)` to the existing
`isMoonshotModel(model) || isZaiModel(model)` branch in
`getModelVariants()` (`src/lib/providers/model-settings.ts:66`), giving
MiMo models the same `instant`/`thinking` variant structure as other
reasoning-capable models.
- Both MiMo models were already registered in `kiloFreeModels` with
`status: 'public'` and the `'reasoning'` flag — the only missing piece
was the opencode variant configuration that tells clients how to toggle
reasoning.

Author: chrarnoldus

src/lib/providers/model-settings.ts

@@ -5,6 +5,7 @@ import { isMoonshotModel } from '@/lib/providers/moonshotai';
 import { isOpenAiModel } from '@/lib/providers/openai';
 import { qwen35_plus_free_model } from '@/lib/providers/qwen';
 import { grok_code_fast_1_optimized_free_model } from '@/lib/providers/xai';
+import { isXiaomiModel } from '@/lib/providers/xiaomi';
 import { isZaiModel } from '@/lib/providers/zai';
 import type {
   CustomLlmProvider,
@@ -62,7 +63,7 @@ export function getModelVariants(model: string): OpenCodeSettings['variants'] {
       efforts.map(effort => [effort, { reasoning: { enabled: effort !== 'none', effort } }])
     );
   }
-  if (isMoonshotModel(model) || isZaiModel(model)) {
+  if (isMoonshotModel(model) || isZaiModel(model) || isXiaomiModel(model)) {
     return {
       instant: { reasoning: { enabled: false } },
       thinking: { reasoning: { enabled: true } },

src/tests/openrouter-models-sorting.approved.json

@@ -189,7 +189,20 @@
       "default_parameters": {},
       "preferredIndex": 3,
       "isFree": true,
-      "opencode": {}
+      "opencode": {
+        "variants": {
+          "instant": {
+            "reasoning": {
+              "enabled": false
+            }
+          },
+          "thinking": {
+            "reasoning": {
+              "enabled": true
+            }
+          }
+        }
+      }
     },
     {
       "id": "anthropic/claude-sonnet-4",
@@ -644,7 +657,20 @@
       ],
       "default_parameters": {},
       "isFree": true,
-      "opencode": {}
+      "opencode": {
+        "variants": {
+          "instant": {
+            "reasoning": {
+              "enabled": false
+            }
+          },
+          "thinking": {
+            "reasoning": {
+              "enabled": true
+            }
+          }
+        }
+      }
     },
     {
       "id": "x-ai/grok-code-fast-1:optimized:free",