[FEATURE]:Build script ignores OPENCODE_MODELS_URL env var #11385

Feature hasn't been suggested before.

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Describe the enhancement you want to request

Description

The runtime respects OPENCODE_MODELS_URL to override the models.dev endpoint (see src/provider/models.ts:84), but the build script in script/build.ts hardcodes https://models.dev/api.json.

This makes it difficult to build in airgapped environments or when using an internal mirror.

Expected behavior

Build script should respect OPENCODE_MODELS_URL like the runtime does.

Current behavior

Build always fetches from https://models.dev/api.json regardless of environment configuration.