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.

benchmark/build.gradle

@@ -60,7 +60,6 @@ dependencies {
     androidTestImplementation libs.androidx.benchmark.junit4
     androidTestImplementation project(path: ':quartz')
     androidTestImplementation project(path: ':commons')
-    androidTestImplementation project(path: ':ammolite')
 
     // Custom C secp256k1 (libschnorr256k1) for the 3-way Android benchmark
     androidTestImplementation libs.schnorr256k1.kmp