build(perf): trim build outputs for hooks, CI, and the shipped font

Headline numbers from a fresh `./gradlew assemble`:
- :commons material_symbols_outlined.ttf 11M -> 409K (subset to the 210
  codepoints actually referenced from MaterialSymbols.kt)
- :amethyst per-ABI APKs no longer built in CI (-PdisableAbiSplits=true);
  ~600M of stripped_native_libs intermediates skipped per run

Changes:
- .git-hooks/pre-push runs only :amethyst:testPlayDebugUnitTest plus jvmTest
  on the KMP modules instead of `./gradlew test`, which was compiling all six
  amethyst variants (play/fdroid x debug/release/benchmark)
- amethyst/build.gradle adds three opt-in fast-build flags:
    -PdisableAbiSplits=true       skip per-ABI APK splits
    -PdisableUniversalApk=true    skip the universal APK output
    -Pamethyst.skipMapping=true   disable R8 (release+benchmark)
  Defaults are unchanged; release pipelines must not set skipMapping.
- .github/workflows/build.yml uses gradle/actions/setup-gradle@v4 with
  cache-read-only on PRs / cache-write on main, drops --no-daemon, collapses
  the Android job to a single Gradle invocation (lint + focused debug unit
  tests + assembleBenchmark with -PdisableAbiSplits=true), and globs both
  APK naming patterns for the upload step.
- tools/material-symbols-subset/{subset.sh,README.md} regenerates the font
  from upstream + MaterialSymbols.kt; run after adding/removing icons.

Verified: ./gradlew :amethyst:help with all three new -P flags parses cleanly,
and ./gradlew :commons:jvmJar --rerun-tasks succeeds with the subsetted font
(commons-jvm jar shrinks from ~13M to 2.9M).

https://claude.ai/code/session_01YSmkagXXN5AwGcY4upiUh1

.git-hooks/pre-push

@@ -12,10 +12,24 @@ echo "$JAVA_HOME"
 echo "$(java -version)"
 echo "Running test... "
 
+# Single-variant pre-push tests. `./gradlew test` would compile six Android
+# variants of :amethyst (play/fdroid × debug/release/benchmark) plus full
+# native-libs merging per variant — ~6× the work of one variant. CI runs the
+# multi-flavor matrix on push to main; pre-push only needs one happy path.
+TASKS=(
+    :quartz:jvmTest
+    :commons:jvmTest
+    :nestsClient:jvmTest
+    :quic:jvmTest
+    :ammolite:testDebugUnitTest
+    :amethyst:testPlayDebugUnitTest
+    :cli:test
+)
+
 if [ "${CLAUDE_CODE_REMOTE:-}" = "true" ]; then
-  ./gradlew test --quiet -x :desktopApp:test -x :desktopApp:upxDownload -x :desktopApp:vlcDownload
+    ./gradlew "${TASKS[@]}" --quiet
 else
-  ./gradlew test --quiet
+    ./gradlew "${TASKS[@]}" :desktopApp:test --quiet
 fi
 status=$?