feat(v1): add event-log summary tool for acceptance evidence

v1/report.py reads events.jsonl and lists each confirmed event with its
latency (flags the 1-3s target) and screenshot, or reports a clean pass
when empty. Supports T-204 latency records and false-alarm counting.
78 tests pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

v1/report.py

@@ -0,0 +1,86 @@
+"""Summarize confirmed fall events for review, latency records and
+false-alarm counting during acceptance sessions.
+
+Reads the JSONL written by ``alerts.EventArtifactWriter``. Use it after a test
+session: run some normal activity (walking, sitting, bending, picking up) and
+check that no events were recorded, or read back the latency of real falls.
+
+    python -m v1.report                      # scans artifacts/events
+    python -m v1.report artifacts/events     # a source directory
+    python -m v1.report .../20260721/events.jsonl
+"""
+
+import json
+import sys
+from pathlib import Path
+from typing import Dict, List
+
+
+def load_events(jsonl_path: Path) -> List[Dict]:
+    path = Path(jsonl_path)
+    if not path.is_file():
+        return []
+    events = []
+    for line in path.read_text(encoding="utf-8").splitlines():
+        line = line.strip()
+        if line:
+            events.append(json.loads(line))
+    return events
+
+
+def collect_jsonl(root: Path) -> List[Path]:
+    """Return every events.jsonl under a source/day directory, or the file itself."""
+
+    path = Path(root)
+    if path.is_file():
+        return [path]
+    return sorted(path.glob("**/events.jsonl"))
+
+
+def summarize(events: List[Dict]) -> Dict:
+    latencies = [float(e.get("latency_seconds", 0.0)) for e in events]
+    within = [lat for lat in latencies if 1.0 <= lat <= 3.0]
+    return {
+        "count": len(events),
+        "latencies": latencies,
+        "latency_in_target": len(within),
+    }
+
+
+def format_report(jsonl_path: Path, events: List[Dict]) -> str:
+    summary = summarize(events)
+    lines = [
+        "{0}".format(jsonl_path),
+        "  events: {0}  (latency in 1-3s: {1}/{0})".format(
+            summary["count"], summary["latency_in_target"]
+        ),
+    ]
+    for event in events:
+        lines.append(
+            "  {0}  track={1}  utc={2}  latency={3:.2f}s  shot={4}".format(
+                event.get("event_id", "?"),
+                event.get("track_id", "?"),
+                event.get("confirmed_at_utc", "?"),
+                float(event.get("latency_seconds", 0.0)),
+                event.get("screenshot", "?"),
+            )
+        )
+    if not events:
+        lines.append("  (no confirmed events — a clean pass for negative activity)")
+    return "\n".join(lines)
+
+
+def main(argv=None) -> int:
+    argv = list(sys.argv[1:] if argv is None else argv)
+    root = Path(argv[0]) if argv else Path("artifacts/events")
+    files = collect_jsonl(root)
+    if not files:
+        print("no events.jsonl found under {0}".format(root))
+        return 0
+    for jsonl_path in files:
+        print(format_report(jsonl_path, load_events(jsonl_path)))
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())