Let the window close, answer stray handshake frames, reply where asked

[krotname]

Summary

• The GUI client could not exit. requestConnectionSettings blocks on a CountDownLatch until Connect or Cancel completes the request. Closing the window only called controller.disconnect(), so the waiting thread stayed parked and the JVM never terminated. windowClosing now completes the pending request exactly like Cancel, which makes ClientGuiController.run dispose and return.
• A stray handshake frame killed the connection. Every misplaced client frame gets a soft Unsupported client frame error, except NAME_REQUEST and USER_NAME, which fell through to default -> throw new IOException(...). Both are now handled with the same soft error, and the switch covers the enum.
• The bot answered in the wrong place. BotChatClient always replied with sendTextMessage, i.e. plain text in the general room: a private command got a public answer, and a command asked inside a room was answered somewhere else. Replies now go back to the room the command came from, or privately to the sender of a private command.
• ci.yml asked setup-gradle for Gradle 8.10.2 while the build runs ./gradlew (wrapper 9.7), so that distribution was downloaded and never used; codeql.yml already omits the pin.

Not changed (needs a decision)

• Rooms restored from the history file at startup are created empty and are only reclaimed once a member leaves, so they occupy maxRooms slots permanently. Whether restored rooms should be pre-created at all, or reclaimed lazily, is a product decision.
• ChatHistoryStore rewrites and fsyncs the whole file per message under a global lock — a durability/throughput trade-off, not an accident.
• The frame rate limiter still parses and answers rejected frames.

Test plan

• ./gradlew spotlessApply check — BUILD SUCCESSFUL (spotless, checkstyle, spotbugs, unit/integration/ui tests, -Werror).
• New tests: BotChatClientTest.answersPrivateCommandsPrivately, answersRoomCommandsInTheSameRoom.

🤖 Generated with Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!