feat(studio): save eval run logs and fix active run status icon

[christso]

Summary

• Capture eval-run stdout/stderr to <run-dir>/console.log and serve it via GET /api/runs/:filename/log (unscoped + benchmark-scoped) so the output survives after the in-memory buffer is pruned, including for runs that crashed early.
• Surface live run status from the in-memory Studio tracker on /api/runs so the RunList renders a pulsing cyan dot for starting/running runs instead of the misleading red ✗ produced when pass_rate is still 0.
• Add a collapsible "Console Log" section in RunDetail with a monospace/dark theme viewer. The section auto-hides when no log is available (remote runs, or local runs that completed before this feature shipped) and live-streams while the run is active.

Closes #1240

Test plan

• bun run typecheck
• bun run lint
• bun run test — 1764 + 67 + 539 tests pass (0 fail)
• Studio frontend builds (bun --filter ./apps/studio run build)
• Red (main): start an eval; the /api/runs entry has pass_rate: 0 so the RunList renders a red ✗; finished runs have no console.log to inspect.
• Green (this branch): launched an eval against /tmp/agentv-uat-1240 via POST /api/eval/run. While running, /api/runs returns "status":"running" and pass_rate: 0 (frontend now renders the pulsing dot). After completion, console.log (2434 bytes) exists in the run dir and GET /api/runs/<id>/log returns the captured output (eval progress + summary). GET /api/runs/<unknown>/log returns 404 → frontend hides the section.

$ curl -s http://localhost:3119/api/runs | jq '.runs[] | {filename, status, pass_rate}'
{
  "filename": "2026-05-14T03-21-04-785Z",
  "status": "running",
  "pass_rate": 0
}

$ curl -s -o /dev/null -w "%{http_code} %{size_download}\n" \
    http://localhost:3119/api/runs/2026-05-14T03-21-04-785Z/log
200 2434

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