fix(llm-model-catalog): stop generated files showing as modified (#4170)

## Summary

Running `pnpm run db:migrate` locally left `defaultPrices.ts` and
`modelCatalog.ts` in `llm-model-catalog` showing as modified every time,
a ~10k-line diff that only ever changed formatting. This stops the
churn.

## Root cause

The root `db:migrate` script ends in `&& turbo run generate`, which runs
the `generate` script in every package that has one, including this one.
The generator writes its output with `JSON.stringify` (quoted keys, no
trailing commas), but the checked-in copies had been reformatted by
oxfmt (unquoted keys, trailing commas). So the generator output never
matched what was committed, even though the parsed data was identical.

## Fix

Add the two generated files to `.oxfmtrc.json`'s ignore list and commit
the raw generator output, matching how other codegen files in the repo
are already handled (e.g. the tsql grammar). Generation is
deterministic, so `generate` and `format` are both no-ops on a clean
tree now.

No changeset: internal package, dev tooling only, no runtime or public
API change.

Author: 1stvamp

.oxfmtrc.json

@@ -22,6 +22,8 @@
     "**/.changeset/",
     "**/dist/",
     "internal-packages/tsql/src/grammar/",
+    "internal-packages/llm-model-catalog/src/defaultPrices.ts",
+    "internal-packages/llm-model-catalog/src/modelCatalog.ts",
     // Maybe turn these on in the future
     "**/*.yaml",
     "**/*.mdx",