Fix agent orchestrator test mock

[hughlv]

Fixes a failing test in src/__tests__/agent.test.ts where module paths and mocked tools were outdated due to a recent refactoring.

Specifically:

• Changed vi.mock('../env.js') and vi.mock('../logger.js') to use ../core/... paths.
• Updated the mock of ../tools/executor.js to mock buildSessionTools (instead of buildExecutorTool) and mapped to the current structure, which returns captureSessionTool and sendToSessionTool.
• Changed buildSetupWorkspaceTool mock to buildWorkspaceTool to reflect ../tools/workspace.js.
• Included the necessary AI SDK properties (steps) to the mock response in the test setup.
• Cleaned up a leftover debug file (vitest_debug.ts).

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PR created automatically by Jules for task 7878726544760059108 started by @hughlv

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