[codex] Add Workshop traces to autoresearch UI

[gabrielnan]

Summary

• add local trace persistence for autoresearch agent steps and evogym runner spans
• forward local runs to Raindrop Workshop without requiring a cloud write key
• surface traces in the tree, inspector, agent sidebar, and Process tab
• keep the evogym UI generic via experiment visualization hooks and artifact media export

Validation

• python3 -m py_compile backend/agent_runtime.py backend/team_journal.py backend/workshop_tracing.py frontend/scripts/export_real_data.py frontend/scripts/serve.py experiments/evogym_walker/loop.py
• git diff --check && git diff --cached --check
• Playwright smoke: /process.html renders, trace chips open trace detail cards, Workshop link is present, no non-404 console errors
• Ran evogym global_searcher, implementor, and verifier under /Users/naka/src/evogym-env/bin/python with RAINDROP_LOCAL_DEBUGGER=http://localhost:5899/v1/; clean local Workshop event ids were recorded

Notes

• Old evogym journal/worktrees were moved under experiments/evogym_walker/archive/20260531T000451Z/ before the fresh run.
• The best evogym frontier improved to official score 2224 during validation.