fix(registry): align publish Lambda timeout with record creation polling budget

## Context

Follow-up from the final review of PR #779. This behavior predates the standalone Agent Registry migration.

## Problem

The registry publish Lambda has a 15-second timeout, while `waitPastCreating` can poll up to 30 times with a 2-second interval, for a nominal 60-second polling budget before SDK-call overhead.

A slow `CreateRegistryRecord` transition can therefore terminate the Lambda before the handler reaches its typed incomplete-publish error path, potentially leaving a DRAFT record that blocks a clean retry through the immutability check.

## Desired outcome

Make the execution budget internally consistent by either:

- Increasing the Lambda timeout to cover the full polling budget plus SDK and cleanup overhead, or
- Redesigning record creation waiting so it does not synchronously occupy the publish Lambda for the full transition.

Preserve actionable reporting for partially created records.

## Acceptance criteria

- The configured execution timeout safely exceeds the maximum synchronous polling duration, or synchronous polling is removed.
- Slow creation cannot terminate before the handler reports the partial record identifier and remediation guidance.
- Tests lock the timeout/poll-budget relationship or exercise the redesigned asynchronous path.
- Normal publish, submit, and optional approval behavior remains unchanged.

## References

- PR #779
- `cdk/src/handlers/shared/registry/agent-registry-client.ts`
- Registry publish Lambda definition in the CDK construct/stack

Start with cdk/src/handlers/shared/registry/agent-registry-client.ts and the registry publish Lambda definition in the CDK construct or stack. Compare the 30-poll, 2-second waitPastCreating budget with the configured Lambda timeout, then inspect PR #779 for context. Done means slow creation cannot terminate before partial-record reporting, the relationship is covered by tests, and normal publish, submit, and approval behavior remains unchanged.

Written by the indexing model from the issue text.