[REMOTE-2409] Make spawned-agent activity and conversation access clear

[warp-agent-staging]

Description

Makes spawned-agent activity and navigation explicit in orchestration transcripts.

• Shows the existing conversation-status activity indicator on child rows while work is active.
• Adds a labeled View action that opens or focuses the child conversation, while keeping disclosure expansion on the chevron and preserving avatar navigation.
• Keeps the parent Warping... signal visible while descendant agents are still working by reusing orchestration-aware status aggregation.
• Tightens waiting-state semantics so a finished child tree does not leave the parent appearing active.

Linked Issue

• REMOTE-2409
• GitHub issue readiness labeling is not applicable; this work was delegated from Linear feedback.
• Screenshots and a full-flow video are included below.

Testing

• ./script/format
• cargo clippy --workspace --exclude warp_completer --all-targets --tests -- -D warnings
• cargo clippy -p warp --all-targets --tests -- -D warnings
• cargo clippy -p warp_completer --all-targets --tests -- -D warnings
• cargo nextest run -p warp --lib --test-threads=1 -E 'test(orchestration_topology::tests) + test(block::view_impl::orchestration::tests)' — 41 passed
• cargo build --bin warp
• Manually tested the dogfood client with a live two-child orchestration flow.

Agent Mode

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

CHANGELOG-IMPROVEMENT: Spawned agents now show active status, keep orchestration progress visible, and provide a direct View action for opening child conversations.

Co-Authored-By: Oz oz-agent@warp.dev

Computer-use screenshots

Computer-use video recordings

View video recording: Starting an agent-mode conversation in the Warp dogfood client that delegates two independent read-only repository questions to child agents, then observing the parent conversation's progress indicator and spawned-agent transcript rows while children are active.

Conversation: https://staging.warp.dev/conversation/43fedaf1-5dc3-4a90-bd51-0533c7dce08d
Run: https://oz.staging.warp.dev/runs/019fb3fc-32e3-77ce-87cf-7e21f0621170
Plans:

• REMOTE-2409 spawned-agent activity and conversation access

This PR was generated with Oz.