chore: sync internal changes (py314 + Kafka Avro message-key)

[yokofly]

Summary

Two commits onto develop:

1. chore: sync internal changes — squashed internal sync.
2. fix(rebase): reconcile py314 + Kafka Avro-key after develop rebase — post-rebase integration fixes so the tip builds against origin/develop, which now carries py314 (migrate embedded CPython to 3.14 with optional free-threaded build #1200) and the Kafka Avro message-key feature (feat(kafka): support Avro-encoded message key via schema registry #1201): ProfileEvents macro continuation, PythonStreamingSource void doCheckpoint signature, and reconstruction of the Avro-key integration onto the parallel Kafka source.

Kafka Avro message-key — broker-backed smoke

Verified end-to-end against a live Redpanda broker + Confluent-compatible schema registry (proton 3.0.26). The read path fetches the key schema by id (GET /schemas/ids/{id}) and emits the decoded record as a JSON string into _tp_message_key; the write path for Avro-encoded keys throws NOT_IMPLEMENTED (read-only) while plaintext-key writes still work.

#	Scenario	Result
1	Value decode (JSONEachRow)	✅ 3 rows
2	Raw _tp_message_key	✅ tenant-a, tenant-b
3	Avro key via schema registry	✅ decoded → {"order_id":42,"region":"us-west"}, {"order_id":99,"region":"eu-central"}
4a	registry-url + JSON value + no key schema	✅ INVALID_SETTING_VALUE
4b	message_key_schema_name + no registry-url	✅ INVALID_SETTING_VALUE
4c	non-String _tp_message_key + avro key	✅ ILLEGAL_COLUMN
5	Write Avro-encoded key	✅ NOT_IMPLEMENTED
+	Raw-key write round-trip	✅ produced key=written-key

Other verification

• unit_tests_dbms Avro / external-stream suites: 33/33 pass (AvroDeserializer, AvroSchemaSerializer, ProtobufMapEntry, ExternalStreamSource, ExternalStreamSettings).
• Full build green (proton + unit_tests_dbms).

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