Reuse cloud skill catalogs across turns until invalidated

[copyberry]

Reuse cloud skill catalogs across turns until invalidated

Why

Cloud skill discovery ran on every turn, even when the Apps resource generation and authentication scope were unchanged.

What changed

• Reuse warning-free catalogs, including empty catalogs, while their authentication scope and Apps resource cache key remain current.
• Refresh after invalidation and retry failed or partial discovery on the next turn.
• Reject discovery results if the Apps resource cache key changes during discovery.

Testing

Update lifecycle tests to verify cached turns avoid catalog listings and skill reads, while connection and authentication changes trigger refreshes. Update the referenced-resource test to verify partial discovery retries on the next turn without an explicit MCP refresh.

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