Remove Scala support (MINOR)

[will-molloy]

Summary

• Remove example-scala module, scalafmt.conf, and all Scala references from build config, version catalog, and README
• No longer using Scala (only Kotlin) and scalafmt keeps breaking across version upgrades

Test plan

• ./gradlew spotlessApply build passes (Java and Kotlin modules unaffected)

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.42%. Comparing base (30f8c94) to head (dc87563).

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #268      +/-   ##
============================================
- Coverage     72.72%   71.42%   -1.30%     
  Complexity        4        4              
============================================
  Files             3        2       -1     
  Lines            11        7       -4     
============================================
- Hits              8        5       -3     
+ Misses            1        0       -1     
  Partials          2        2              

Flag	Coverage Δ
integration-tests-macos-latest	80.00% <ø> (ø)
integration-tests-ubuntu-latest	80.00% <ø> (ø)
integration-tests-windows-latest	80.00% <ø> (ø)
unit-tests-macos-latest	71.42% <ø> (-1.30%)	⬇️
unit-tests-ubuntu-latest	71.42% <ø> (-1.30%)	⬇️
unit-tests-windows-latest	71.42% <ø> (-1.30%)	⬇️

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