Add centralized pipeline results JSON storage (Issue #4)

Creates /pipeline-results/ directory and writes a structured JSON file
after each CI run (before notification), capturing branch, commit,
actor, timestamp, result, test counts, features, duration, and tags.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ci-runner.sh

@@ -266,6 +266,39 @@ print(f'Report written to $REPORT_FILE')
   echo "Failure report: $REPORT_FILE"
 fi
 
+# ─── Write Pipeline Result JSON ───
+RESULTS_DIR="$SCRIPT_DIR/pipeline-results"
+RESULT_TIMESTAMP=$(date -u +%Y-%m-%dT%H:%M:%SZ)
+RESULT_FILENAME=$(date -u +%Y-%m-%d_%H%M%S)_${BRANCH}.json
+RESULT_FILE="$RESULTS_DIR/$RESULT_FILENAME"
+mkdir -p "$RESULTS_DIR"
+python3 -c "
+import json, sys
+
+result = {
+    'branch': '$BRANCH',
+    'commit': '$COMMIT',
+    'actor': '$ACTOR',
+    'timestamp': '$RESULT_TIMESTAMP',
+    'result': '$OVERALL',
+    'tests': {
+        'passed': int('$PASS_COUNT' or 0),
+        'failed': int('$FAIL_COUNT' or 0),
+        'skipped': int('$SKIP_COUNT' or 0),
+        'deselected': int('$DESELECTED_COUNT' or 0),
+        'errors': int('$ERROR_COUNT' or 0),
+    },
+    'features': '$FEATURES_RESULT',
+    'duration_seconds': int('$DURATION' or 0),
+    'tags_tested': '$TAGS_USED',
+    'trigger_source': '$ACTOR',
+}
+
+with open('$RESULT_FILE', 'w') as f:
+    json.dump(result, f, indent=2)
+print(f'Pipeline result written: $RESULT_FILE')
+" 2>&1
+
 # ─── Send Notification ───
 bash "$SCRIPT_DIR/ci-notify.sh" \
   "$BRANCH" "$COMMIT" "$OVERALL" "$SUMMARY" "$FEATURES_RESULT" "${DURATION}s" "$ACTOR" "$REPORT_FILE" "$SUITE_INFO"