Add comprehensive test coverage for MCPConnectionPool connection lifecycle

[Copilot]

Why

• The MCPConnectionPool singleton and its connection lifecycle management lacked test coverage for critical failure scenarios

How

• Added 22 unit tests covering all connection lifecycle operations:
  • Singleton behavior: Initialization, thread-safety, event loop management
  • Connection cleanup: Idle timeout (15min), rate-limited passive cleanup (2min intervals)
  • Connection verification: Stale connection detection (2min idle threshold), parallel verification with recreation
  • Parallel operations: Concurrent connection creation, partial failure handling
  • Error handling: Connection failures, timeout enforcement, graceful degradation
  • Tool caching: Cache updates, invalidation on disconnect, mapping integrity
  • Connection management: Touch mechanism, reuse optimization, proper closure (close() vs aexit)

Tests

• All 22 tests pass in 2.4s
• Used configurable timeout constants (IDLE_MARGIN_SECONDS=10) to prevent timing-related flakiness
• Mock specifications prevent fragile attribute access patterns
• CodeQL analysis: 0 security vulnerabilities

Notes

• Test execution optimized from 60s to 2.4s by using dynamic timeout adjustment in timeout tests
• No changes to production code—pure test coverage addition

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[github-actions]

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clarifai.cli	58%	➖
clarifai.cli.templates	46%	❌
clarifai.client	67%	➖
clarifai.client.auth	67%	➖
clarifai.constants	100%	✔
clarifai.datasets	100%	✔
clarifai.datasets.export	80%	✔
clarifai.datasets.upload	75%	➖
clarifai.datasets.upload.loaders	37%	❌
clarifai.models	100%	✔
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clarifai.runners	52%	➖
clarifai.runners.models	58%	➖
clarifai.runners.pipeline_steps	41%	❌
clarifai.runners.pipelines	77%	➖
clarifai.runners.utils	62%	➖
clarifai.runners.utils.data_types	72%	➖
clarifai.schema	100%	✔
clarifai.urls	60%	➖
clarifai.utils	60%	➖
clarifai.utils.evaluation	67%	➖
clarifai.workflows	95%	✔
Summary	61% (8883 / 14463)	➖

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