Allow specifying custom BYOK known model list

[dolfies]

Currently, the list of models supported by BYOK is hosted at a hardcoded URL on the VSCode CDN. This makes contributing to or configuring the list of models quite difficult.

This PR adds a simple option to allow users to point the list to a URL of their choosing (e.g. a gist), for customizability and aiding development.

[dolfies]

@microsoft-github-policy-service agree

[Copilot]

Pull request overview

Adds a user-configurable setting to override the BYOK “known models” JSON endpoint (previously hardcoded to a VS Code CDN URL), enabling custom model lists (e.g., via a gist) to be used by BYOK providers.

Changes:

• Introduces a new configuration key for the BYOK model info URL with a default pointing to the existing CDN JSON.
• Updates BYOK provider registration flow to fetch the known model list from the configured URL.
• Exposes the new setting in package.json and localizes its description in package.nls.json.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/platform/configuration/common/configurationService.ts	Adds ConfigKey.BYOKModelInfoUrl configuration key with a default CDN URL.
src/extension/byok/vscode-node/byokContribution.ts	Reads the configured URL and uses it when fetching the BYOK known model list.
package.nls.json	Adds localized description string for the new setting.
package.json	Contributes github.copilot.chat.byok.modelInfoUrl to the extension’s settings.

[dolfies]

Are there any blockers on a review here?