Add extract worker configuration controls

internal/core/config/env.go

@@ -36,6 +36,18 @@ func (c *Config) applyEnvOverridesWithLookup(lookup func(string) (string, bool))
 		}
 		c.Concurrency.TotalLLM = value
 	}
+	if raw, ok := lookup("NOTARIUS_STAGE_WORKERS_EXTRACT"); ok {
+		value, err := parseIntEnv("NOTARIUS_STAGE_WORKERS_EXTRACT", raw)
+		if err != nil {
+			return err
+		}
+		if c.Concurrency.StageWorkers == nil {
+			c.Concurrency.StageWorkers = make(map[string]int)
+		}
+		c.Concurrency.StageWorkers["extract"] = value
+		c.Concurrency.extractWorkersConfigured = true
+	}
+	c.Concurrency.recomputeStageWorkerDefaults()
 	if raw, ok := lookup("NOTARIUS_WORK_DIR"); ok {
 		c.Diagnostics.WorkDir = strings.TrimSpace(raw)
 	}