feat(soak): artifacts, graceful shutdown, health probes, smoke script, v3.3.4

Batched remaining harness tasks (27-30, 33):

Task 27 — Artifact capture on failure: screenshots, HTML snapshots,
game state JSON, and console error tails are captured into
tests/soak/artifacts/<run-id>/ when a scenario throws. Successful
runs get a summary.json. Old runs (>7d) are pruned on startup.

Task 28 — Graceful shutdown: first SIGINT/SIGTERM flips the abort
signal (scenarios finish current turn then unwind). 10s after, a
hard-kill fires if cleanup hangs. Double Ctrl-C = immediate exit.
Exit codes: 0 success, 1 errors, 2 interrupted.

Task 29 — Periodic health probes: every 30s GET /health against the
target server. Three consecutive failures abort the run with
health_fatal, preventing staging outages from being misattributed
to harness bugs. Corrected endpoint from /api/health to /health
per server/routers/health.py.

Task 30 — Smoke test script: tests/soak/scripts/smoke.sh, a 60s
end-to-end canary that health-probes the target, seeds if needed,
and runs one minimal populate game.

Task 33 — Version bump to v3.3.4: both index.html footers (was
v3.1.6), new footer added to admin.html (had none), pyproject.toml.

Also fixes discovered during stress testing:
- SessionPool sets baseURL on all contexts so relative goto('/')
  resolves correctly between games (was "invalid URL" error)
- RoomCoordinator key is now unique per game-start (Date.now
  suffix) so Deferred promises don't carry stale room codes from
  previous games

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/soak/scripts/smoke.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+# Soak harness smoke test — end-to-end canary against local dev.
+# Expected runtime: ~60 seconds.
+set -euo pipefail
+
+cd "$(dirname "$0")/.."
+
+: "${TEST_URL:=http://localhost:8000}"
+: "${SOAK_INVITE_CODE:=SOAKTEST}"
+
+echo "Smoke target: $TEST_URL"
+echo "Invite code:  $SOAK_INVITE_CODE"
+
+# 1. Health probe
+curl -fsS "$TEST_URL/api/health" > /dev/null || {
+  echo "FAIL: target server unreachable at $TEST_URL"
+  exit 1
+}
+
+# 2. Ensure minimum accounts
+if [ ! -f .env.stresstest ]; then
+  echo "Seeding accounts..."
+  bun run seed -- --count=4
+fi
+
+# 3. Run minimum viable scenario
+TEST_URL="$TEST_URL" SOAK_INVITE_CODE="$SOAK_INVITE_CODE" \
+  bun run soak -- \
+    --scenario=populate \
+    --accounts=2 \
+    --rooms=1 \
+    --cpus-per-room=0 \
+    --games-per-room=1 \
+    --holes=1 \
+    --watch=none
+
+echo "Smoke PASSED"