### Bug Description #### Problem 1 Launchpad fails to parse many `platforms` definitions. We need to complete https://github.com/canonical/craft-platforms/issues/5 and sync with the Launchpad team to consume that build planner. #### Problem 2 The legacy remote builder would only allow snaps that could build a single artefact on a `build-on` architecture. That is an architecture could only appear once in all `build-on` entries. The new remote builder doesn't restrict this. This is a problem because Launchpad's API appears not to distinguish between `build-on` and `build-for`, so it is not clear Snapcraft can request builds. ### To Reproduce snapcraft remote-build --platform amd64 ### Environment n/a ### snapcraft.yaml ```shell name: remote-build-platforms-error version: "1.0" summary: test description: test confinement: strict base: core24 platforms: amd64: build-on: amd64 arm64: build-on: amd64 parts: my-part: plugin: nil ``` ### Relevant log output ```shell Multiple builds match the current platform. Recommended resolution: Check the "--platform" and "--build-for" parameters. ``` ### Additional context _No response_