## Summary
Adds a dedicated `codex.sandbox_outcome` telemetry event so we can query
sandbox edge outcomes without threading sandbox metadata through
tool-result output types.
This is meant to make sandbox failures and approved escalation retries
visible in OTEL while keeping the existing `codex.tool_result` event
shape focused on tool completion data.
## What changed
- Adds `SessionTelemetry::sandbox_outcome(...)`, which emits
`codex.sandbox_outcome` as both a log and trace event.
- Records the tool name, call id, sandbox outcome, initial attempt
duration, and escalated attempt duration when a retry runs.
- Emits `denied` when the sandbox blocks execution and no retry is run.
- Emits `timed_out` and `signal` when those sandbox errors surface from
tool execution.
- Emits `escalated` when the initial sandboxed attempt fails and the
approved unsandboxed retry succeeds.
- Adds OTEL coverage for the new event payload, including timing fields.
## Validation
- `RUST_MIN_STACK=8388608 just test -p codex-core
sandbox_outcome_event_records_outcome
handle_sandbox_error_user_approves_retry_records_tool_decision`
- `just test -p codex-otel
otel_export_routing_policy_routes_tool_result_log_and_trace_events
runtime_metrics_summary_collects_tool_api_and_streaming_metrics`
- `just fix -p codex-core`
- `just fix -p codex-otel`
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