Tighten v0 project compatibility follow-ups #2592

Description

Address the remaining actionable review feedback from #2575 without expanding the compatibility architecture. The v1 CLI should delegate v0 deployment to the latest v0 release, preserve the resolved AWS region during that handoff, avoid emitting an empty translated tool-runtime collection, and keep one source of truth for v0-only fields.

Acceptance Criteria

• v0 deployment uses @aws/agentcore@0 rather than a fixed patch version.
• the v1-resolved region is forwarded to delegated v0 deployment, including first deployment with no configured targets.
• an empty v0 mcpRuntimeTools array does not produce toolRuntimes: [].
• v0-only collections are retained only in legacy.v0Spec, without a duplicate LegacyExtras copy.
• focused and full test suites pass.

Additional Context

Follow-up to the review threads on #2575. Targeted guidance for removed v0 commands will be handled separately once the replacement wording is agreed.