Record reasoning replay removal metrics (#61017)

## What changed

Parse reasoning removals from response `input_transformations` and carry the counts through completion events to sampling telemetry.

- Add `codex.responses.reasoning_replay` to distinguish unavailable reports, no reported removals, prefix mismatches, and other removals.
- Add `codex.responses.reasoning_items_removed` histograms by bounded removal reason, grouping unknown or missing reasons under `other`.
- Include zero counts for usable reports; exclude missing, null, or malformed reports from histograms without failing the response.
- Use the sampling step's session telemetry when recording response events.

## Testing

Add SSE and WebSocket integration coverage for report availability, removal counts, unknown reasons, zero observations, and `product_sku` tags in exported metrics.

GitOrigin-RevId: 83c70ca6067fa4b34bf5c463958b4632a7a0a188

codex-rs/codex-api/tests/sse_end_to_end.rs

@@ -174,6 +174,7 @@ async fn responses_stream_parses_items_and_completed_end_to_end() -> Result<()>
             response_id,
             token_usage,
             usage_metadata,
+            reasoning_removals: _,
             end_turn,
         } => {
             assert_eq!(response_id, "resp1");