Add load test harness for pool and fleet sizing

Adds the scripts used to size the connection pool and validate fleet polling under load: burst arrival and mixed workload drivers, pool and resource samplers, a UI probe, host seed/drop SQL, and a gevent Dockerfile. Hosts are addressed by compose service name (api:5001) rather than a local path, so the harness runs against any stack rather than one machine.

loadtest_token.py mints a scoped collector token named LOADTEST and prints the secret once, then revokes only that token by name so a real collector token is never touched. envkeyfallback is false, so the harness needs a genuine managed token rather than an env key.

scripts/loadtest/ui_probe.py

@@ -0,0 +1,78 @@
+"""Measure UI latency against the API, independent of any load generator.
+
+WHY separate from poll_fleet.py: when the probe shares an event loop with the
+simulated fleet, generator-side scheduling can starve the probe and produce UI
+latencies that are an artifact of the harness rather than of the server. Run
+this in its own container, concurrently with the fleet, so the two cannot
+interfere.
+
+Usage:
+    python ui_probe.py --seconds 90 --interval 1.0
+"""
+import argparse
+import json
+import ssl
+import statistics
+import time
+import urllib.request
+
+
+def percentile(values, fraction):
+    if not values:
+        return 0.0
+    ordered = sorted(values)
+    index = min(int(len(ordered) * fraction), len(ordered) - 1)
+    return ordered[index]
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--seconds', type=int, default=90)
+    parser.add_argument('--interval', type=float, default=1.0)
+    parser.add_argument('--url',
+                        default='https://api:5001/api/dashboard/health')
+    parser.add_argument('--timeout', type=float, default=120.0)
+    arguments = parser.parse_args()
+
+    context = ssl.create_default_context()
+    context.check_hostname = False
+    context.verify_mode = ssl.CERT_NONE
+
+    durations = []
+    failures = {}
+    deadline = time.monotonic() + arguments.seconds
+
+    while time.monotonic() < deadline:
+        started = time.monotonic()
+        try:
+            request = urllib.request.Request(arguments.url)
+            with urllib.request.urlopen(
+                    request, timeout=arguments.timeout,
+                    context=context) as response:
+                response.read()
+                if response.status == 200:
+                    durations.append(time.monotonic() - started)
+                else:
+                    key = str(response.status)
+                    failures[key] = failures.get(key, 0) + 1
+        except Exception as error:
+            key = type(error).__name__
+            failures[key] = failures.get(key, 0) + 1
+        remaining = arguments.interval - (time.monotonic() - started)
+        if remaining > 0:
+            time.sleep(remaining)
+
+    print(json.dumps({
+        'ui_samples': len(durations) + sum(failures.values()),
+        'ui_ok_200': len(durations),
+        'ui_failures': failures,
+        'ui_median_ms': round(statistics.median(durations) * 1000, 1)
+                        if durations else None,
+        'ui_p95_ms': round(percentile(durations, 0.95) * 1000, 1)
+                     if durations else None,
+        'ui_max_ms': round(max(durations) * 1000, 1) if durations else None,
+    }, indent=2))
+
+
+if __name__ == '__main__':
+    main()