Route handler-level parse errors back to peer instead of completing client futures

[jkschneider]

Summary

• HeaderDelimitedMessageHandler.receive() returned JsonRpcError.invalidRequest(...) for frame and parse failures on inbound messages, and JsonRpc.bind() treated every JsonRpcError as a peer response. Combined with PR Fix silent hang when deserialization fails with no request id #14's extractId() recovering an id from malformed bytes where possible, this gave two silent failure modes:

• if the extracted id collided with an open client request, that unrelated client future was completed exceptionally with the peer's malformed message treated as a wire error response;

• if the extracted id was null (the more common case), the "Error with no id" branch in JsonRpc.bind failed every open client future at once.

In neither case was the actual error sent back to the peer that produced the malformed message.

This PR:

• Introduces JsonRpcReceiveException (extends IOException) carrying the recovered id + JsonRpcError.Detail. Both delimited handlers now throw it for frame/parse failures rather than returning a JsonRpcError.
• Adds a catch in JsonRpc.bind() that forks the error response back to the peer; openRequests is left untouched.
• Brings NewLineDelimitedMessageHandler to symmetric error semantics: distinguishes mid-message EOF (peer died with partial bytes — throws EOFException) from parse failure on a complete frame (throws JsonRpcReceiveException with id extraction where possible).
• Extracts the previously private extractId recovery logic from HeaderDelimitedMessageHandler into a package-private IdExtractor so both handlers share it.

Test plan

• ./gradlew test — all 22 tests pass (1 pre-existing @Disabled)
• JsonRpcTest.malformedInboundDoesNotCompleteOpenClientRequests — new regression test demonstrating the fix. Verified by neutralizing the new catch in JsonRpc.bind and observing the test fail (no error response sent to peer), then restoring.
• NewLineDelimitedMessageHandlerTest — new test class (the handler had no tests previously); covers happy path, EOF between messages, mid-message EOF, malformed JSON in a complete frame, and id extraction from a partial frame.
• HeaderDelimitedMessageHandlerTest.receiveStillReturnsInvalidRequestForNonEmptyMalformedHeader renamed to receiveThrowsForNonEmptyMalformedHeader and updated to assert the new throw contract.