fix(compute): deliver the Haiku geo profile to ECS agents

## Problem

The ECS backend never sets `ANTHROPIC_DEFAULT_HAIKU_MODEL` in `cdk/src/constructs/ecs-agent-cluster.ts`. As a result, `agent/src/config.py` falls back to the hardcoded `us.anthropic.claude-haiku-4-5-20251001-v1:0` profile.

On deployments configured with a non-US `bedrockGeoRegion`, the ECS task role grants the resolved geography but the auxiliary model still calls the US profile. This can fail with `AccessDenied` and contradicts the `resolveBedrockGeoRegion` JSDoc in `cdk/src/constructs/bedrock-models.ts`, which says the main and auxiliary models cannot route through different geographies. The later `haikuInferenceProfileId` JSDoc records this ECS exception.

## Expected behavior

Pass the resolved `haikuInferenceProfileId` to the ECS container as `ANTHROPIC_DEFAULT_HAIKU_MODEL`, matching AgentCore and Lambda MicroVM delivery. Add a synth assertion for a non-US geography.

Refs #764

Start in cdk/src/constructs/ecs-agent-cluster.ts and trace how the resolved haikuInferenceProfileId is delivered to ECS containers; compare the AgentCore and Lambda MicroVM delivery paths. Review the related JSDoc in cdk/src/constructs/bedrock-models.ts, then add a synth assertion for a non-US bedrockGeoRegion. Done means ECS sets ANTHROPIC_DEFAULT_HAIKU_MODEL to the resolved profile.

Written by the indexing model from the issue text.