Fix drawboard rendering for axis-aligned shapes

[sainadh777]

Summary

• complete maintained TODO item 90.1 for the WebSocket drawboard example
• render axis-aligned rectangle and ellipse messages as lines, matching HTML5 Canvas behavior
• add regression coverage for both shape types
• remove the completed TODO and add a changelog entry

Rationale and impact

A zero-width or zero-height rectangle/ellipse is not rendered by the Java2D implementation used by the drawboard example, while the browser canvas renders the corresponding user gesture as a line. The change is confined to the example application and preserves existing behavior for non-axis-aligned shapes.

Validation

• ant validate — BUILD SUCCESSFUL
• ant test -Dtest.entry=org.apache.tomcat.websocket.TestDrawMessage — BUILD SUCCESSFUL; 2 tests, 0 failures, 0 errors, 0 skipped
• ant clean — BUILD SUCCESSFUL
• ant — BUILD SUCCESSFUL
• ant test on macOS — did not qualify: Tribes multicast tests failed with NoRouteToHostException; rerun in isolated Linux as required
• initial Linux source-transfer run — discarded because macOS extended attributes materialized as AppleDouble ._*.jar files
• first clean Linux ant test run — completed but did not qualify after the Colima VM clock corrected forward by about 13 hours mid-run, producing unrelated timeout/rate-window failures and an impossible 788-minute Ant duration
• stable-clock Linux ant clean && ant test on eclipse-temurin:25-jdk-noble (ARM64) — BUILD SUCCESSFUL in 29m59s; 651 suite summaries, no failed suites; standard native/OpenSSL-dependent skips only
• generated-distribution smoke test on the same tested build in a Docker --init container — HTTP 200 from http://127.0.0.1:8080/ (11,229 bytes); shutdown.sh stopped Tomcat and the JVM PID was reaped

Tested and pushed commit: 63bd5f30e892eb93d536a2ee27b3948c28d1b829.