[FEATURE] Add latest model aliases for model setting in settings.json

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

The model field in settings.json and managed-settings.json requires a specific model ID (claude-sonnet-4-6[1m] for example). When a new model releases every user and org with a pinned default must manually update their settings files, for MDM-managed deployments pushing managed-settings.json to an organization this means a full redeploy cycle to keep the default current.

Proposed Solution

Support family alises like sonnet-latest, haiku-latest, or opus-latest that resolve to the most recent stable version at session start. Equivalents compatible with Vertex AI should be included as well.

Alternative Solutions

Manually updating managed-settings.json after each release works but requires ongoing maintenance.

Using a SessionStart hook to rewrite the config is a hacky workaround.

Priority

Low - Nice to have

Feature Category

Configuration and settings

Use Case Example

My team manages claude code via MDM. We push managed-settings.json org wide to pin a default model. Every time Anthropic releases a new sonnet version, for example, we have to manually update and redeploy the config to all machines. Instead we could use sonnet-latest to keep ourselves on the most up to date model and forget about updating by hand.

The same problem occurs to individual users who pin a default in their settings.json

Additional Context

A latest alias is a fairly common pattern in other tools like docker image tags and npm latest. This would be consistent with how developers expect version pinning to work.