feat(ai): add Xiaomi MiMo provider (#4005)

* fix(ai): include minimax-cn in cross-provider-handoff matrix

* feat(ai): add Xiaomi MiMo provider

Adds Xiaomi MiMo as an openai-completions-compatible provider.

- packages/ai: register provider in types/KnownProvider, env-api-keys (XIAOMI_API_KEY), generate-models, models.generated.ts, overflow util, README, CHANGELOG
- packages/ai/test: extend stream, tokens, abort, empty, context-overflow, overflow, image-tool-result, tool-call-without-result, total-tokens, unicode-surrogate, cross-provider-handoff matrices with Xiaomi
- packages/coding-agent: default model (mimo-v2.5-pro), display name (Xiaomi MiMo), CLI env var docs, README, docs/providers.md

closes #3912

---------

Co-authored-by: Mario Zechner <badlogicgames@gmail.com>

packages/ai/CHANGELOG.md

@@ -2,11 +2,17 @@
 
 ## [Unreleased]
 
+<<<<<<< feat/add-xiaomi-provider
+### Added
+
+- Added Xiaomi MiMo provider (openai-completions compatible) with `XIAOMI_API_KEY` authentication.
+=======
 ## [0.71.1] - 2026-05-01
 
 ### Added
 
 - Added `websocket-cached` transport support for OpenAI Codex Responses used with ChatGPT subscription auth. This keeps the same WebSocket open for a session and, after the first request, sends only new conversation items instead of resending the full chat history when possible.
+>>>>>>> main
 
 ## [0.71.0] - 2026-04-30