fix(cdk): conditionally pass harnesses prop for CDK construct compat

[notgitika]

Summary

Fixes e2e http-gateway-targets.test.ts failure on both npm and main CDK variants.

Preview's vended cdk-stack.ts passes harnesses to AgentCoreApplication, but the npm-published @aws/agentcore-cdk package doesn't have this prop in its TypeScript interface. With strict: true, the CDK app fails to compile during synth, producing no stack — then deploy errors with NoStack: CloudFormationStack object does not hold a stack.

Fix: build the AgentCoreApplication props dynamically and cast, so the harnesses property is only present when harnesses are actually configured.

Test plan

• E2E http-gateway-targets.test.ts passes on both npm and main variants

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	43.54%	10037 / 23049
🔵	Statements	42.8%	10665 / 24913
🔵	Functions	40.4%	1692 / 4188
🔵	Branches	40.28%	6513 / 16166

Generated in workflow #2959 for commit 4be00c4 by the Vitest Coverage Report Action

[agentcore-cli-automation]

Fix looks correct — pragmatic workaround for the npm-published @aws/agentcore-cdk not yet exposing harnesses in its props type. Snapshot is in sync with the vended file. No blocking issues from my side.

One minor observation (non-blocking): the // eslint-disable-next-line @typescript-eslint/no-explicit-any comment on line 60/62 sits above const appProps: Record<string, unknown> = { spec };, but the as any it's meant to silence is on the new AgentCoreApplication(...) line a few lines below. Today this is harmless because src/assets is excluded from this repo's ESLint and the vended CDK project has no lint script — but if a downstream user adds linting with @typescript-eslint/no-explicit-any enabled, the comment won't disable the right line. Easy follow-up: move the comment directly above this.application = new AgentCoreApplication(...), or keep the original prop literal and just append as any to it (which would be shorter overall).

Worth considering a TODO/FIXME pointing at this so it can be ripped out once the npm package gains the harnesses prop.