fix(audit): require integer phase0 summary row limits

Require non-negative integer maxSessions/maxChannels/maxSkipReasons in summary core and both phase0 summary/capture CLIs to prevent silent flooring of fractional values. Architecture/protocol diagrams reviewed; no flow or API shape changes required.

scripts/capture-phase0-live-baseline.ts

@@ -45,9 +45,9 @@ function usage(): string {
     '  --sample-out <path>                     Output JSONL sample path override',
     '  --summary-json-out <path>               Output summary JSON path override',
     '  --summary-md-out <path>                 Output summary markdown path override',
-    '  --max-sessions <number>                 Limit session rows in output (default: 20)',
-    '  --max-channels <number>                 Limit channel rows in output (default: 20)',
-    '  --max-skip-reasons <number>             Limit skip reason rows in output (default: 10)',
+    '  --max-sessions <integer>                Limit session rows in output (default: 20)',
+    '  --max-channels <integer>                Limit channel rows in output (default: 20)',
+    '  --max-skip-reasons <integer>            Limit skip reason rows in output (default: 10)',
   ].join('\n');
 }
 
@@ -125,6 +125,20 @@ function parseOptionalNumber(raw: string | undefined, flag: string): number | un
   return parsed;
 }
 
+function parseOptionalInteger(raw: string | undefined, flag: string): number | undefined {
+  const parsed = parseOptionalNumber(raw, flag);
+  if (parsed === undefined) {
+    return undefined;
+  }
+  if (!Number.isInteger(parsed)) {
+    throw new Error(`Invalid ${flag} value "${raw}". Expected an integer.`);
+  }
+  if (parsed < 0) {
+    throw new Error(`${flag} must be greater than or equal to 0.`);
+  }
+  return parsed;
+}
+
 function parseBackendTargets(raw: string | undefined): Phase0BackendTarget[] | undefined {
   const values = parseCsv(raw);
   if (!values) {
@@ -237,9 +251,9 @@ async function main(): Promise<void> {
   const summaryOptions: Phase0BaselineSummaryOptions = {
     channels,
     sources,
-    maxSessions: parseOptionalNumber(values['max-sessions'], '--max-sessions') ?? 20,
-    maxChannels: parseOptionalNumber(values['max-channels'], '--max-channels') ?? 20,
-    maxSkipReasons: parseOptionalNumber(values['max-skip-reasons'], '--max-skip-reasons') ?? 10,
+    maxSessions: parseOptionalInteger(values['max-sessions'], '--max-sessions') ?? 20,
+    maxChannels: parseOptionalInteger(values['max-channels'], '--max-channels') ?? 20,
+    maxSkipReasons: parseOptionalInteger(values['max-skip-reasons'], '--max-skip-reasons') ?? 10,
   };
 
   const backendRouteEvents = backendTargets && backendTargets.length > 0