fix(docs): restore dual COMPUTE.md references in COST_MODEL.md

The original had COMPUTE.md listed twice intentionally — once for
the network architecture section and once for compute billing. Restore
this pattern instead of merging into one entry.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: scottschreckengaust

docs/design/COST_MODEL.md

@@ -89,8 +89,9 @@ For multi-user deployments, cost should be attributable to individual users and
 
 ## Reference
 
-- [COMPUTE.md](./COMPUTE.md) -- VPC infrastructure cost breakdown, compute option billing models.
+- [COMPUTE.md - Network architecture](./COMPUTE.md) -- VPC infrastructure cost breakdown.
 - [ORCHESTRATOR.md](./ORCHESTRATOR.md) -- Polling cost analysis.
+- [COMPUTE.md](./COMPUTE.md) -- Compute option billing models.
 - [OBSERVABILITY.md](./OBSERVABILITY.md) -- Cost-related metrics (`agent.cost_usd`, token usage).
 - [Deployment guide](../guides/DEPLOYMENT_GUIDE.md) -- Deployment choices, scale-to-zero analysis, AWS services inventory.
 - [DEPLOYMENT_ROLES.md](./DEPLOYMENT_ROLES.md) -- Least-privilege IAM policies for deployment.