Accept cloud environments without a pinned docker image

[warp-dev-github-integration]

Description

The Warp client failed to deserialize cloud environments whose stored JSON omits the docker_image field. AmbientAgentEnvironment.base_image was a flattened, required BaseImage enum, so when the docker_image key was absent serde could not match any enum variant and deserialization failed. The server can store environments that do not pin a base image, so the client must load them.

This change makes base_image an Option<BaseImage> with #[serde(default, flatten, skip_serializing_if = "Option::is_none")]:

• Environments without docker_image now deserialize to None instead of erroring.
• Environments with a pinned image keep the exact existing wire format ({"docker_image": "..."}) — the flattened enum behavior is unchanged.
• Serializing an environment with no image omits the docker_image key, so the format round-trips.

Call sites that read base_image for display or assignment were updated to handle the Option: the CLI environment command (environment get/list/update), the environments settings page, the conversation details panel, and the environment context-chip sidecar. None renders as an empty/None display string in those surfaces, matching how other optional fields are shown.

Linked Issue

• The linked issue is labeled ready-to-spec or `ready-to-implement.
• Where appropriate, screenshots or a short video of the implementation are included below.

No linked issue — this is a deserialization robustness fix for server-stored cloud environments that lack a base image.

Testing

Added unit tests in crates/cloud_object_models/src/cloud_environment_tests.rs:

• deserialize_environment_without_docker_image — an environment with no docker_image key loads and base_image is None.
• environment_without_docker_image_preserves_other_fields — description, code_forge, source_repos, and secrets still deserialize correctly when docker_image is absent.
• serialize_environment_without_docker_image_omits_field — serializing a None base image does not emit a docker_image key.
• serialize_environment_with_docker_image_preserves_wire_format — an environment with an image still serializes to a top-level "docker_image" string (not a nested object), preserving the existing wire format.
• roundtrip_serde_without_docker_image — serialize → deserialize is stable and the JSON contains no docker_image key.

Validation run locally:

• cargo test -p cloud_object_models — 29 passed, 0 failed.

• cargo clippy -p cloud_object_models --all-targets --all-features --tests -- -D warnings — clean.

• cargo check -p warp --lib — clean.

• ./script/format --check — clean.

• cargo clippy -p warp --all-targets --tests -- -D warnings (CI default-features configuration) — clean.

• I have manually tested my changes locally with ./script/run

Screenshots / Videos

Not applicable — no user-visible UI behavior change beyond no longer failing to load environments that lack a base image.

Agent Mode

• Warp Agent Mode - This PR was created via Warp's AI Agent Mode

CHANGELOG-BUG-FIX: Cloud environments that do not pin a docker image no longer fail to load in the Warp client.

Conversation: https://staging.warp.dev/conversation/4dd52438-2846-4326-bbd5-40866bdacaae
Run: https://oz.staging.warp.dev/runs/019f5d57-1af7-78a3-b386-bbaf841dcd0f

This PR was generated with Oz.