Add Dev Container terminal sessions

[s-zaizen]

Description

Adds feature-flagged Dev Container terminal sessions.

This lets users open a repository with a Dev Container config and launch Warp inside that
container from:

• the repository open prompt
• the new-session Dev Container submenu
• the /dev-container slash command

The implementation reuses Warp's local TTY shell starter path. Warp resolves the devcontainer
CLI from the user's shell PATH, runs devcontainer up, then enters the selected config with
devcontainer exec and starts the normal Warp bash bootstrap.

Dev Container sessions also show a Docker-styled prompt chip and sidebar/session indicators.

Linked Issue

Closes #4460

Related:

• Support container workflows #6129

• Add devcontainers feature so it can easily be included in remote dev envs #6164

• Add a devcontainer for Warp repository development #9413

• more visual cue for ssh/docker/native tab #7709

• 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
  (especially for user-visible or UI changes).

Testing

• git diff --check
• cargo fmt --check
• cargo clippy -p warp --lib --tests -- -D warnings
• cargo test -p warp dev_container --lib
• cargo test -p warp test_open_repository_with_devcontainer_shows_open_prompt_toast --lib

Manual:

• Built and opened WarpLocal.app

• Opened a repository with a Dev Container config

• Verified the Dev Container prompt appears

• Verified Open in Dev Container launches an in-container terminal session

• Verified the left sidebar uses the Docker icon for the Dev Container session

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

Screenshots / Videos

warp-devcontainer.mp4

Agent Mode

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

Changelog Entries for Stable

CHANGELOG-NEW-FEATURE: Added Dev Container terminal sessions that let users open repositories with
Dev Container configs directly in Warp.

[oz-for-oss]

@s-zaizen

This PR is not linked to an issue that is marked with ready-to-implement.

Issue-state enforcement details:

• Associated same-repo issues checked: Warp for DevContainers #4460

• Required readiness label: ready-to-implement

Readiness check:

• Warp for DevContainers #4460: missing ready-to-implement; readiness labels present: none

To continue, link this PR to a same-repo issue such as Closes #123 in the PR description, and make sure that issue has ready-to-implement.

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[oz-for-oss]

@s-zaizen

This PR is not linked to an issue that is marked with ready-to-implement.

Issue-state enforcement details:

• Associated same-repo issues checked: #4460

• Required readiness label: ready-to-implement

Readiness check:

• #4460: missing ready-to-implement; readiness labels present: none

To continue, link this PR to a same-repo issue such as Closes #123 in the PR description, and make sure that issue has ready-to-implement.

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