fix(paired): bound arbiter interventions to stop infinite arbiter loop

The owner↔reviewer↔arbiter loop could repeat forever: when the arbiter
ruled PROCEED/REVISE/RESET it reset round_trip_count to 0, and nothing
tracked how many times the arbiter had already intervened. A re-deadlock
re-invoked the arbiter without bound.

Add a persistent arbiter_intervention_count (new column + migration 020)
that survives the round-trip reset, and a configurable cap
ARBITER_MAX_INTERVENTIONS (default 1). Once the arbiter has intervened
that many times and the loop still deadlocks, requestArbiterOrEscalate
escalates straight to the user instead of re-invoking the arbiter.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/paired-execution-context-arbiter.ts

@@ -78,9 +78,19 @@ export function handleArbiterCompletion(args: {
   const { task, taskId, summary } = args;
   const now = new Date().toISOString();
   const arbiterVerdict = classifyArbiterVerdict(summary);
+  // Persist a running count of arbiter interventions so the loop can be bounded.
+  // This must NOT be reset by the round_trip_count reset below — otherwise the
+  // owner↔reviewer loop could re-trigger the arbiter without limit.
+  const nextArbiterInterventionCount =
+    (task.arbiter_intervention_count ?? 0) + 1;
 
   logger.info(
-    { taskId, arbiterVerdict, summary: summary?.slice(0, 200) },
+    {
+      taskId,
+      arbiterVerdict,
+      arbiterInterventionCount: nextArbiterInterventionCount,
+      summary: summary?.slice(0, 200),
+    },
     'Arbiter verdict rendered',
   );
 
@@ -98,6 +108,7 @@ export function handleArbiterCompletion(args: {
           owner_step_done_streak: 0,
           finalize_step_done_count: 0,
           empty_step_done_streak: 0,
+          arbiter_intervention_count: nextArbiterInterventionCount,
           arbiter_verdict: arbiterVerdict,
           arbiter_requested_at: null,
         },
@@ -121,12 +132,17 @@ export function handleArbiterCompletion(args: {
           owner_step_done_streak: 0,
           finalize_step_done_count: 0,
           empty_step_done_streak: 0,
+          arbiter_intervention_count: nextArbiterInterventionCount,
           arbiter_verdict: arbiterVerdict,
           arbiter_requested_at: null,
         },
       });
       logger.info(
-        { taskId, arbiterVerdict },
+        {
+          taskId,
+          arbiterVerdict,
+          arbiterInterventionCount: nextArbiterInterventionCount,
+        },
         'Arbiter requested owner changes — resuming owner flow',
       );
       return;