webui: fix ?model= URL param race in router mode

[ServeurpersoCom]

Overview

Fixes automatic model selection with the URL query parameter ?model=xxx

Additional information

Initial fix without refactoring, cc @alek, This is just the race fix and I tested it in router mode.
But I'm sure we can do better in terms of architecture so as not to have any race at all. And we can also add alias support.

fix-model-url-param-race.mp4

Solve #22324

Requirements

• I have read and agree with the contributing guidelines
• AI usage disclosure: YES Opus 4.7 + local MCP rootless disposable pod with shared GPU

[ServeurpersoCom]

We could assign the store sole responsibility for fetching at startup, and it would be the source of truth for everything else. This applies to both the query parameter and the automatic selection of the currently loaded model.

[allozaur]

We could assign the store sole responsibility for fetching at startup, and it would be the source of truth for everything else. This applies to both the query parameter and the automatic selection of the currently loaded model.

yeah, in general i am re-reviewing some of the ways we initialize some of the stores/services and i'd consider doing what u suggest as well. but for this PR let's focus only on solving the race condition