fix GUI interaction edge cases and build checks

[perNyfelt]

What changed

• Fix console EOF, default-value, date-range, and selection handling.
• Make Swing and JavaFX headless/resource-display behavior consistent.
• Make JavaFX clipboard writes synchronous when called on the FX thread.
• Correct URL probing, resource lookup, and filename parsing edge cases.
• Update Matrix BOM to 2.5.1 and swing-widgets to 1.1.2.
• Repair the check and release scripts and configure SpotBugs with runtime dependencies.
• Add focused console, utility, and headless UI tests and update documentation.

Why

The review found inconsistent cancellation contracts, unhandled EOF/null inputs, missing classpath resources, asynchronous clipboard behavior, and a build that could not reliably run quality checks.

Validation

• ./gradlew test --no-configuration-cache
• ./gradlew spotlessApply check --no-configuration-cache
• bash -n check.sh release.sh
• git diff --check