ci: capture UI (Playwright) per-test counts (ci_test_runs) (#12915)

## What

Capture **UI (Playwright) per-test counts** in the `ci_test_runs`
OpenObserve stream — `tests_total/passed/failed/flaky/skipped` per run.

This was meant to land in #12914 but missed that squash-merge (pushed
just after), so it's its own PR now. Companion: o2-enterprise#2046.

## How
- `playwright.yml` merge job gains a `stats` output (from the merged
`report.json`).
- `report_to_openobserve` reads it and emits the test-count fields via a
small generic **`EXTRA_JSON`** merge hook added to `o2-run-report.sh`.
- Non-fatal as before; no-ops when secrets are unset.

API (pytest) counts are not included (would need `--junitxml` + XML
aggregation — separate change).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

.github/scripts/o2-run-report.sh

@@ -8,6 +8,10 @@
 # shared o2-report.sh. Live re-runs append one doc per attempt; dashboards keep the latest
 # attempt per run_id (row_number() dedup), so retries become an attribute, not duplicate rows.
 #
+# Optional EXTRA_JSON (env): a JSON OBJECT the caller can pass to fold extra fields into the run
+# doc (e.g. test-case counts). Shallow-merged via jq `*` (EXTRA_JSON keys win on conflict). On any
+# parse/merge error the base payload is kept unchanged.
+#
 # Never fails the workflow: missing secrets or any API/ingest error only warns.
 set -uo pipefail
 : "${STREAM:?STREAM required}"
@@ -73,4 +77,14 @@ printf '%s' "$RUN_JSON" | jq \
      retry_wasted_sec: (($total-$final)|round)
    }' > "$PAYLOAD_FILE" 2>/dev/null || { echo "::warning::payload build failed"; exit 0; }
 
+# Optional EXTRA_JSON: shallow-merge caller-supplied fields into the doc (e.g. test counts).
+# On any merge error, keep the base payload (never fail the report).
+if [ -n "${EXTRA_JSON:-}" ] && printf '%s' "$EXTRA_JSON" | jq -e . >/dev/null 2>&1; then
+  if jq -s '.[0] * .[1]' "$PAYLOAD_FILE" <(printf '%s' "$EXTRA_JSON") > "$PAYLOAD_FILE.m" 2>/dev/null; then
+    mv "$PAYLOAD_FILE.m" "$PAYLOAD_FILE"
+  else
+    echo "::warning::EXTRA_JSON merge failed — keeping base payload"; rm -f "$PAYLOAD_FILE.m"
+  fi
+fi
+
 bash "$(dirname "$0")/o2-report.sh" "$STREAM" "$PAYLOAD_FILE"