GeezerVison

Fixes #766.

Binary AMQP messages currently serialize extensions as bare application-property names, while the reader only accepts cloudEvents:-prefixed names. For example, a traceparent or custom extension disappears after a writer/Proton encode/decode/reader round trip.

Prefix the fallback extension names in ProtonAmqpMessageWriter, as required by the AMQP binding's primary mapping. Correct the existing writer expectations and add real wire round-trip coverage for CloudEvents 0.3 and 1.0, including traceparent, tracestate, and a custom extension. The tests use no payload to isolate this change from #761.

Validation:

• Before the fix: 4 of 20 writer tests failed, including both new round trips.
• After the fix: MAVEN_OPTS=-Xmx384m ./mvnw -B -ntp -pl amqp -am verify -Dmaxmemory=256m passed with 136 tests (API 8, core 90, AMQP 38), plus all three modules' Javadocs.
• git diff --check passed. No live broker or full-repository integration suite was run.

AI assistance was used to investigate, implement, and test this change.