chore: clean up .gitignore, track gradle-wrapper.jar, drop .zcode/

- Rewrite .gitignore with proper sections; add ignores for common
  Android/IDE/OS artifacts (*.so, *.hprof, app/release/, Thumbs.db,
  .vscode/, *.swp).
- Track gradle/wrapper/gradle-wrapper.jar so ./gradlew works after a
  fresh clone (the previous negation rule was a no-op without a prior
  *.jar ignore, so the jar was never committed).
- Stop tracking the local .zcode/ tooling directory (kept on disk).

.gitignore

@@ -1,17 +1,42 @@
-*.iml
-.gradle/
-.idea/
-.kotlin/
-local.properties
-.DS_Store
-build/
-captures/
-.externalNativeBuild/
-.cxx/
+# Built application files
 *.apk
 *.aab
 *.ap_
 *.dex
 
-# Keep the gradle wrapper jar (it IS the build tool bootstrap).
+# Build output (Gradle / AGP)
+build/
+.gradle/
+.kotlin/
+captures/
+
+# Native build artifacts
+.externalNativeBuild/
+.cxx/
+*.so
+
+# IDE / Editor
+*.iml
+.idea/
+.vscode/
+*.swp
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Local config (machine-specific SDK path, signing keys, etc.)
+local.properties
+
+# Profiling / heap dumps
+*.hprof
+
+# Release build output
+app/release/
+
+# Local tooling (ZCode session/plans — not part of the project)
+.zcode/
+
+# Gradle wrapper: the jar IS the build bootstrap and must be committed so
+# `./gradlew` works after a fresh clone. Keep it despite any broad ignores above.
 !gradle/wrapper/gradle-wrapper.jar