[codex] Stream Codex sub-agents as tool calls

[boudra]

Summary

• Map Codex collabAgentToolCall items into canonical sub-agent tool_call timeline items.
• Correlate child Codex thread notifications back to the parent sub-agent tool call.
• Build sub-agent log and actions from the existing activity curator format so live child activity appears inside the parent tool call detail.

Why

Codex app-server already emits sub-agent lifecycle items and child-thread events, but Paseo was not projecting them as canonical tool calls. That made Codex sub-agent work less visible than Claude task/sub-agent work and caused the parent agent to look idle without a visible in-progress sub-agent call.

Validation

• npx vitest run packages/server/src/server/agent/activity-curator.test.ts packages/server/src/server/agent/providers/codex/tool-call-mapper.test.ts packages/server/src/server/agent/providers/codex-app-server-agent.test.ts --bail=1
• npm run lint
• npm run build --workspace @getpaseo/highlight && npm run typecheck --workspace @getpaseo/server

Note: after rebasing, npm install refreshed dependencies but its prepare hook failed because global core.hooksPath is set to /dev/null. Building the highlight workspace made server typecheck pass.