[APP-4491] Allow cloud agent view exit during long commands

[harryalbert]

Description

Cloud-mode panes can now exit agent view even while the active block is a long-running third-party agent command. The generic local-terminal guard still blocks exiting fullscreen agent view during local long-running commands, but Cloud Agent entries and ambient cloud-mode terminal views bypass that guard and either pop nested cloud panes or exit root cloud agent view in place.

Linked Issue

APP-4491

• 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

• cargo fmt --all --check
• cargo clippy -p warp --lib --all-targets -- -D warnings
• cargo test -p warp escape_exits_root_cloud_agent_view_with_long_running_command
• cargo test -p warp escape_pops_nested_cloud_agent_view_with_long_running_command
• cargo test -p warp escape_does_not_exit_local_agent_view_with_long_running_command
• I have manually tested my changes locally with ./script/run

Agent Mode

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

CHANGELOG-BUG-FIX: Fixed cloud mode panes getting stuck in agent view while a third-party agent command is still running.

This PR was created by Oz (running Codex).