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.

.claude/CLAUDE.md

@@ -46,8 +46,7 @@ amethyst/
 │       └── jvmAndroid/    # Opus encode/decode, AudioRecord/AudioTrack
 ├── desktopApp/     # Desktop JVM application (layouts, navigation)
 ├── amethyst/       # Android app (layouts, navigation)
-├── cli/            # Amy — non-interactive CLI (JVM only, no Compose)
-└── ammolite/       # Support module (unused)
+└── cli/            # Amy — non-interactive CLI (JVM only, no Compose)
 ```
 
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