fix(agents): surface native runs in Agents panel

[LordMerc]

What changed

Native T3-managed AgentRuns now publish their lifecycle into the existing parent-thread Agents panel path.

• shows native spawned runs live in the parent Agents panel
• displays resolved model, profile ID, and shortened run ID
• keeps follow-up, waiting, cancellation, success, and failure states synchronized
• treats panel activities as a best-effort projection so they cannot corrupt authoritative AgentRun state

This is a stacked fix for pingdotgg#5632 and targets agent/native-agent-orchestration.

Why

The first-class agent_spawn path persists AgentRuns separately from provider-native task.* activities. The Agents panel only folds parent-thread task activities, so successful T3-managed child runs previously rendered as “No agents yet.”

UI evidence

Before

After

Evidence is published on a separate branch so binary artifacts do not enter the product diff.

Verification

• vp test run apps/server/src/agents/AgentOrchestrationLive.test.ts apps/server/src/agents/run/AgentRunReactor.test.ts packages/client-runtime/src/state/subagentRuntime.test.ts — 76 tests passed
• scoped server, client-runtime, and web typechecks passed
• targeted formatting and git diff --check passed
• integrated browser smoke: Claude spawned environment/sol-smoke-test; Agents panel showed gpt-5.6-sol · profile sol-smoke-test · run 91a6da73; child completed successfully

Implemented with GPT-5.6 through the Codex harness in T3 Code.

[megascan]

Reviewed and integrated—thank you. The core change is now on the target branch as ab6d31f with your authorship preserved. I added 61e0858 on top to preserve Effect interruption in the best-effort activity projection and to label native follow-up activations as turns, avoiding two different
un\ labels in one row.\n\nVerification on the integrated branch:\n- 28 focused server tests passed\n- 49 client-runtime fold tests passed\n- server, client-runtime, and web typechecks passed\n- targeted lint and formatting passed\n\nI am closing this stacked PR because its changes are incorporated into pingdotgg#5632.