test(harvest): add live integration test suite

[TheRealAgentK]

Background

Harvest was migrated to SDK 2.0.0 in #276 with 42 new unit tests, but no tests/test_harvest_integration.py was added.

Harvest uses platform OAuth, so e2e coverage requires a manually obtained access token. This is more friction than custom-auth integrations, but still valuable — schema-validation crashes (the kind that bit #289 google-sheets and #290 xero in production) only surface against real responses.

Acceptance criteria

• harvest/tests/test_harvest_integration.py following the writing-integration-tests skill
• At minimum read-only smoke coverage for the major resource families: time entries, projects, clients, tasks, users
• Destructive tests (create_time_entry, update_time_entry, delete_time_entry, stop_time_entry) gated with @pytest.mark.destructive
• Token-extraction recipe documented at the top of the test file (how to obtain HARVEST_ACCESS_TOKEN and HARVEST_ACCOUNT_ID from a sandbox account)
• pytest harvest/ -m integration passes locally

Related

• feat(harvest): upgrade SDK to 2.0.0, add pytest unit tests #276 (SDK 2.0.0 upgrade)

[TheRealAgentK]

CLosed via #276