Update orchestration message transcript UI

[kjankov]

Description

• Updates successful orchestration send/receive messages to render as transcript-style rows with the agent avatar beside the message content instead of boxed status cards.
• Uses the orchestrator avatar for the lead/parent agent, existing harness/provider logos for known child agents, and distinct fallback child avatars for Oz/unknown child agents.
• Persists child harness metadata so orchestration avatars can be restored consistently.

Linked Issue

• Linear: QUALITY-594 Send message/received message UI
• 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).

Screenshots / Videos

Not included.

Testing

• cargo fmt
• cargo fmt --check
• git --no-pager diff --check
• cargo test -p warp orchestration --lib
• cargo test -p warp hidden_child --lib
• cargo clippy --workspace --all-targets --all-features --tests -- -D warnings

Agent Mode

• Warp Agent Mode - This PR was created via Warp's AI Agent Mode
• Conversation: https://app.warp.dev/conversation/1b48f020-21b0-4b7b-a0e5-7274863bab36
• Plan: https://app.warp.dev/drive/notebook/R5oEvNd2TWKKGqNoBVs9zE

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

[oz-for-oss]

@kjankov

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[oz-for-oss]

Overview

This PR updates successful orchestration send/receive messages to render as transcript rows with participant avatars and persists child harness metadata for avatar restoration.

Concerns

• Multiple received-message transcript rows reuse the same collapsible state, so every row chevron controls the whole message group instead of its own row.
• For faster review, please upload screenshots or a video of the UI change working end to end.

Verdict

Found: 0 critical, 1 important, 1 suggestion

Request changes

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[oz-for-oss]

⚠️ [IMPORTANT] Every received-message row passes the same output message_id, so multiple row chevrons share one hover/collapse state and clicking any row collapses or expands every message body; keep a single group-level chevron or register per-message state before rendering per-row toggles.