[REMOTE-1752] Show cloud orchestration pills for child runs

[seemeroland]

Summary

• Anchor shared-session orchestration polling on the parent run when a user opens a cloud child run directly.
• Reuse the opened child conversation, synthesize/link the parent orchestrator conversation, and register siblings so the existing pill bar can render the full orchestration tree.
• Add a regression test covering direct child-run opening while keeping that child selected.

Tests

• cargo fmt --check
• git diff --check
• cargo check -p warp --tests
• cargo clippy -p warp --tests
• cargo test -p warp terminal::shared_session::viewer::orchestration_viewer_model::tests::direct_child_viewer_anchors_pill_tree_on_parent_run -- --exact

This PR was created by Oz (running Codex).