Small tweaks to prepare for FIM usage

[EamonNerbonne]

• FIM api endpoint for codestral #2912
• limit max_tokens to ensure we don't just keep on streaming junk when the LLM gets dizzy
• mark some readonly stuff thusly.

[changeset-bot]

⚠️ No Changeset found

Latest commit: e4caf37

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR