Fix MySQL CDC hang when SSH tunnel dies

[ilidemi]

When SSH connection dies during CDC, the keepalive machinery notices but BinlogSyncer is not aware. To make it aware, close SSH connection besides just the MySQL query connection. Add tests for hangs in mystream.GetEvent() and syncer.Close() (both observed in production). Verified that without the fix both tests fail.

[codecov]

❌ 2 Tests Failed:

Tests completed	Failed	Passed	Skipped
1977	2	1975	234

View the top 2 failed test(s) by shortest run time

github.com/PeerDB-io/peerdb/flow/e2e::TestGenericBQ

Stack Traces | 0s run time

=== RUN   TestGenericBQ
=== PAUSE TestGenericBQ
=== CONT  TestGenericBQ
--- FAIL: TestGenericBQ (0.00s)

github.com/PeerDB-io/peerdb/flow/e2e::TestGenericBQ/Test_Inheritance_Table_With_Dynamic_Setting

Stack Traces | 33.5s run time

=== RUN   TestGenericBQ/Test_Inheritance_Table_With_Dynamic_Setting
=== PAUSE TestGenericBQ/Test_Inheritance_Table_With_Dynamic_Setting
=== CONT  TestGenericBQ/Test_Inheritance_Table_With_Dynamic_Setting
2026/03/19 05:24:28 INFO fetched schema x-peerdb-additional-metadata={Operation:FLOW_OPERATION_UNKNOWN} table=e2e_test_mychclg_tttlev1s.test_simple_schema_changes
    generic_test.go:1085: UNEXPECTED STATUS TIMEOUT STATUS_SNAPSHOT
    bigquery.go:86: begin tearing down postgres schema bq_ch5nrtia_20260319052428
--- FAIL: TestGenericBQ/Test_Inheritance_Table_With_Dynamic_Setting (33.46s)

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[github-actions]

🔄 Flaky Test Detected

Analysis: The test failed due to "context deadline exceeded" when connecting to the Temporal server — a transient infrastructure/network timeout, not a code logic failure.
Confidence: 0.95

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[github-actions]

🔄 Flaky Test Detected

Analysis: Multiple Snowflake e2e tests failed with "UNEXPECTED STATUS TIMEOUT STATUS_SETUP", indicating transient connectivity/availability issues with the external Snowflake service during flow initialization, unrelated to the partitioned table column-ordering code change.
Confidence: 0.92

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[github-actions]

🔄 Flaky Test Detected

Analysis: The e2e test TestGenericBQ/Test_Inheritance_Table_With_Dynamic_Setting timed out during the STATUS_SNAPSHOT phase, which is a classic flaky failure caused by timing-sensitive infrastructure (Temporal/snapshot workflow) rather than a code regression.
Confidence: 0.92

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