Hardening: CI + templates + contributor docs

.github/ISSUE_TEMPLATE/bug_report.md

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+---
+name: Bug report
+about: Create a report to help us improve
+labels: bug
+---
+**Describe the bug**
+A clear and concise description.
+
+**Reproduction**
+Code snippet / dataset shape / Spark & Scala versions.
+
+**Expected behavior**
+
+**Environment**
+- Scala:
+- Spark:
+- JVM:
+- Module:
+
+**Additional context**
+Logs / stacktrace.

.github/ISSUE_TEMPLATE/feature_request.md

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+---
+name: Feature request
+about: Suggest an idea
+labels: enhancement
+---
+**Problem**
+
+**Proposed solution**
+
+**Alternatives**
+
+**Additional context**

.github/ISSUE_TEMPLATE/question.md

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+---
+name: Question
+about: Ask a usage question
+labels: question
+---
+**Your question**
+
+**Context**
+Spark/Scala versions, sample code.

.github/PULL_REQUEST_TEMPLATE.md

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+### Summary
+
+### Type
+- [ ] Bug fix
+- [ ] Feature
+- [ ] Docs
+- [ ] Build/CI
+
+### Compatibility
+Spark: [ ] 3.4  [ ] 3.5
+Scala: [ ] 2.12  [ ] 2.13
+
+### Checklist
+- [ ] Added/updated tests
+- [ ] Updated docs
+- [ ] Ran `sbt clean test` locally

.github/dependabot.yml

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+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule: { interval: "weekly" }
+  - package-ecosystem: "sbt"
+    directory: "/"
+    schedule: { interval: "weekly" }

.github/workflows/scala-ci.yml

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+name: Scala CI
+on:
+  pull_request:
+  push:
+    branches: [ master, main ]
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        scala: [2.12.18, 2.13.13]
+        spark: [3.4.3, 3.5.1]
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '11'
+      - name: Cache Ivy/Coursier
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.ivy2/cache
+            ~/.cache/coursier
+            ~/.sbt
+          key: ${{ runner.os }}-ivy-${{ hashFiles('**/*.sbt','project/**') }}
+      - name: Create local.sbt overrides
+        run: |
+          echo 'ThisBuild / scalaVersion := "${{ matrix.scala }}"' > local.sbt
+          echo 'ThisBuild / crossScalaVersions := Seq("2.12.18","2.13.13")' >> local.sbt
+          echo 'val sparkVer = "${{ matrix.spark }}"' >> local.sbt
+      - name: Test
+        run: sbt -v clean test

CONTRIBUTING.md

@@ -1,215 +1,21 @@
-# Contributing to Generalized K-Means Clustering
+# Contributing
 
-Thank you for your interest in contributing to this project! This document provides guidelines for contributing to the generalized K-means clustering library.
-
-## Development Environment Setup
-
-### Prerequisites
-
-- **Java 17** or higher
-- **SBT 1.x** (Scala Build Tool)
-- **Scala 2.12.18** (managed by SBT)
-- **Apache Spark 3.4.0** (managed by SBT)
-
-### Getting Started
-
-1. **Clone the repository:**
-   ```bash
-   git clone https://github.com/derrickburns/generalized-kmeans-clustering.git
-   cd generalized-kmeans-clustering
-   ```
-
-2. **Compile the project:**
-   ```bash
-   sbt compile
-   ```
-
-3. **Run tests:**
-   ```bash
-   sbt test
-   ```
-
-4. **Check code style:**
-   ```bash
-   sbt scalastyle
-   ```
-
-## Code Style Guidelines
-
-### Scala Style
-
-- Follow standard Scala naming conventions
-- Use 2-space indentation
-- Line length should not exceed 120 characters
-- Use meaningful variable and function names
-- Add scaladoc documentation for all public APIs
-
-### Code Quality
-
-- **Linting:** Run `sbt scalastyle` before submitting
-- **Testing:** Ensure all tests pass with `sbt test`
-- **Coverage:** Maintain or improve test coverage
-- **Dependencies:** Check for dependency updates with `sbt dependencyUpdates`
-
-### Error Handling
-
-- Use `ValidationUtils` for common validation patterns
-- Provide meaningful error messages with context
-- Handle edge cases gracefully
-- Use SLF4J logging instead of print statements
-
-## Project Structure
-
-```
-src/
-├── main/scala/com/massivedatascience/
-│   ├── clusterer/          # Core clustering algorithms
-│   ├── divergence/         # Bregman divergence implementations  
-│   ├── linalg/            # Linear algebra utilities
-│   ├── transforms/        # Data transformation utilities
-│   └── util/              # Common utilities and validation
-└── test/scala/com/massivedatascience/
-    └── clusterer/         # Test suites
-```
-
-## Architecture Overview
-
-### Core Components
-
-- **BregmanDivergence**: Defines distance functions for clustering
-- **BregmanPointOps**: Point operations and factory methods
-- **KMeansModel**: Trained model with prediction capabilities
-- **MultiKMeansClusterer**: Interface for different clustering implementations
-
-### Key Design Patterns
-
-- **Weighted Vectors**: All operations use `WeightedVector` for weighted clustering
-- **Pluggable Distance Functions**: Easy addition of new Bregman divergences
-- **Iterative Training**: Multi-stage training support
-
-## Testing
-
-### Test Requirements
-
-- All new features must include comprehensive tests
-- Tests should cover edge cases and error conditions
-- Use ScalaTest framework with the existing `LocalClusterSparkContext` trait
-- Test files should be in `src/test/scala/com/massivedatascience/clusterer/`
-
-### Running Tests
+## Dev setup
+- Java 11 (Temurin)
+- sbt 1.10.x
+- Scala 2.12/2.13 (cross-build)
+- Spark 3.4/3.5 (provided)
 
+## Building
 ```bash
-# Run all tests
-sbt test
-
-# Run specific test suite
-sbt "testOnly *KMeansSuite"
-
-# Run with coverage
-sbt coverage test coverageReport
-```
-
-## Pull Request Process
-
-### Before Submitting
-
-1. **Ensure all tests pass:**
-   ```bash
-   sbt test
-   ```
-
-2. **Check code style:**
-   ```bash
-   sbt scalastyle
-   ```
-
-3. **Update documentation** if you've made API changes
-
-4. **Add tests** for new functionality
-
-### Pull Request Guidelines
-
-- **Title**: Use descriptive titles (e.g., "Add validation for negative weights in BregmanPointOps")
-- **Description**: Clearly explain what changes you made and why
-- **Testing**: Describe how you tested your changes
-- **Breaking Changes**: Clearly mark any breaking changes
-
-### Commit Message Format
-
-Use conventional commit messages:
-
-```
-type(scope): brief description
-
-Longer description if needed
-
-- List specific changes
-- Include reasoning for complex changes
+sbt +compile
+sbt +test
 ```
 
-**Types:**
-- `feat`: New feature
-- `fix`: Bug fix
-- `docs`: Documentation changes
-- `style`: Code style changes
-- `refactor`: Code refactoring
-- `test`: Adding or updating tests
-- `perf`: Performance improvements
-
-## Common Development Tasks
-
-### Adding a New Bregman Divergence
-
-1. Create a new trait or object extending `BregmanDivergence`
-2. Implement required methods: `convex`, `convexHomogeneous`, `gradientOfConvex`, `gradientOfConvexHomogeneous`
-3. Use `ValidationUtils` for input validation
-4. Add comprehensive tests in the test suite
-5. Update documentation
-
-### Improving Performance
-
-1. Profile your changes using appropriate tools
-2. Add benchmarks if introducing performance-critical code
-3. Consider memory usage and garbage collection impact
-4. Test with realistic data sizes
-
-### Adding Configuration Options
-
-1. Add new options to `KMeansConfig` if applicable
-2. Ensure backward compatibility
-3. Add validation for new configuration values
-4. Document the new options
-
-## Code Review Criteria
-
-### Code Quality
-- [ ] Code follows project style guidelines
-- [ ] Error handling is appropriate and consistent
-- [ ] No code duplication
-- [ ] Performance considerations addressed
-
-### Testing
-- [ ] Adequate test coverage
-- [ ] Tests cover edge cases
-- [ ] Tests are maintainable and readable
-
-### Documentation
-- [ ] Public APIs are documented
-- [ ] Complex algorithms are explained
-- [ ] Breaking changes are clearly marked
-
-## Getting Help
-
-- **Issues**: Check existing [GitHub issues](https://github.com/derrickburns/generalized-kmeans-clustering/issues)
-- **Discussions**: Start a discussion for questions about implementation
-- **Code Review**: Request review from maintainers
-
-## License
-
-By contributing to this project, you agree that your contributions will be licensed under the Apache License 2.0.
-
-## Recognition
-
-Contributors will be acknowledged in release notes and the project README.
+## Releasing
+- Tag `vX.Y.Z` and let CI publish (if configured).
+- Keep CHANGELOG up to date.
 
-Thank you for contributing to the generalized K-means clustering library!
+## Code style
+- Scalafmt recommended; enforce in CI if added.
+- PRs must pass CI and tests.

README_BADGES_SNIPPET.md

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+<!-- Badges: paste near the top of README.md -->
+[![Scala CI](https://github.com/OWNER/REPO/actions/workflows/scala-ci.yml/badge.svg)](https://github.com/OWNER/REPO/actions/workflows/scala-ci.yml)
+[![License](https://img.shields.io/badge/License-Apache_2.0-blue.svg)](LICENSE)

SECURITY.md

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+# Security Policy
+Report vulnerabilities via GitHub Security Advisories.
+We triage within 7 days and aim to patch critical issues within 30 days.

local.sbt.example

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+// Copy to local.sbt to override versions locally (git-ignored)
+ThisBuild / scalaVersion := "2.13.13"
+ThisBuild / crossScalaVersions := Seq("2.12.18","2.13.13")
+val sparkVer = "3.5.1"