build: remove unused :ammolite module

The :ammolite module contained no production Kotlin/Java sources (just
a manifest, build.gradle, and proguard stubs) and no module in the
codebase imports com.vitorpamplona.ammolite.*.

Removes:
- ammolite/ directory (5 files)
- :ammolite project include in settings.gradle
- implementation project(':ammolite') from :amethyst
- androidTestImplementation project(':ammolite') from :benchmark
- :ammolite:testDebugUnitTest from CI workflow and pre-push hook
- -keep class com.vitorpamplona.ammolite.** rules from
  :amethyst, :commons, and :desktopApp proguard files
- Stale references in CONTRIBUTING.md, CLAUDE.md, and the
  gradle-expert skill dependency-graph doc

Small build-graph win: one fewer module to configure, compile, lint,
and spotless-check on every build, and one fewer unit-test target in
both CI and the local pre-push hook.

desktopApp/compose-rules.pro

@@ -70,7 +70,6 @@
 # JSON-mapped first-party types (mirrors mobile)
 -keep class com.vitorpamplona.quartz.** { *; }
 -keep class com.vitorpamplona.amethyst.** { *; }
--keep class com.vitorpamplona.ammolite.** { *; }
 
 # ============================================================================
 # Desktop-only JNI keep rules — libraries the mobile module doesn't ship