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/config/load-config.ts

@@ -244,6 +244,7 @@ export function loadConfig(): AppConfig {
       ),
       agentLanguage: readText('AGENT_LANGUAGE') ?? '',
       arbiterDeadlockThreshold: readInteger('ARBITER_DEADLOCK_THRESHOLD', 2),
+      arbiterMaxInterventions: readInteger('ARBITER_MAX_INTERVENTIONS', 1),
       maxRoundTrips,
     },
     models: {

src/config/schema.ts

@@ -57,6 +57,7 @@ export interface AppConfig {
     forceFreshClaudeReviewerSessionInUnsafeHostMode: boolean;
     agentLanguage: string;
     arbiterDeadlockThreshold: number;
+    arbiterMaxInterventions: number;
     maxRoundTrips: number;
   };
   models: {