refactor: unify brand to 'CompressKit' and enhance project configuration

## Brand Unification
- Update all repository references to 'LessUp/compress-kit'
- Rename project title from 'Encoding' to 'CompressKit'
- Update all documentation URLs to lessup.github.io/compress-kit/
- Update VitePress base URL to /compress-kit/

## Development Tools
- Add .clang-format for C++ code formatting (Google Style)
- Add requirements.txt for Python dependency tracking
- Add .github/dependabot.yml for automated dependency updates
- Add .github/workflows/codeql.yml for security scanning

## Documentation
- Document Range Coder >500KB performance limitation
- Update OpenSpec specifications with brand consistency requirements

## Build System
- Add 'make format' command for code formatting
- Add 'make lint' command for code linting
- Improve clean target to include Range coder Rust artifacts

## AI Tooling
- Create project-level CLAUDE.md with project-specific instructions
- Update AGENTS.md with brand guidelines and known limitations

Author: LessUp

.clang-format

@@ -0,0 +1,20 @@
+# Based on Google C++ Style Guide
+# https://google.github.io/styleguide/cppguide.html
+
+BasedOnStyle: Google
+IndentWidth: 4
+UseTab: Never
+ColumnLimit: 100
+AllowShortFunctionsOnASingleLine: Inline
+AllowShortIfStatementsOnASingleLine: Never
+AllowShortLoopsOnASingleLine: false
+BreakBeforeBraces: Attach
+IndentCaseLabels: false
+SpaceBeforeParens: ControlStatements
+PointerAlignment: Left
+DerivePointerAlignment: false
+
+# For this educational project
+CommentPragmas: ''
+SortIncludes: true
+IncludeBlocks: Regroup

.github/dependabot.yml

@@ -0,0 +1,50 @@
+# Dependabot configuration for automated dependency updates
+# https://docs.github.com/en/code-security/dependabot/dependabot-version-updates
+
+version: 2
+updates:
+  # Go modules
+  - package-ecosystem: "gomod"
+    directory: "/algorithms/huffman/go"
+    schedule:
+      interval: "monthly"
+    open-pull-requests-limit: 5
+
+  - package-ecosystem: "gomod"
+    directory: "/algorithms/arithmetic/go"
+    schedule:
+      interval: "monthly"
+    open-pull-requests-limit: 5
+
+  - package-ecosystem: "gomod"
+    directory: "/algorithms/range/go"
+    schedule:
+      interval: "monthly"
+    open-pull-requests-limit: 5
+
+  - package-ecosystem: "gomod"
+    directory: "/algorithms/rle/go"
+    schedule:
+      interval: "monthly"
+    open-pull-requests-limit: 5
+
+  # Rust cargo
+  - package-ecosystem: "cargo"
+    directory: "/algorithms/range/rust"
+    schedule:
+      interval: "monthly"
+    open-pull-requests-limit: 5
+
+  # Node.js (documentation site)
+  - package-ecosystem: "npm"
+    directory: "/"
+    schedule:
+      interval: "monthly"
+    open-pull-requests-limit: 5
+
+  # GitHub Actions
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "monthly"
+    open-pull-requests-limit: 5

.github/workflows/ci.yml

@@ -265,8 +265,9 @@ jobs:
 
       - name: Test Range coder correctness
         run: |
-          # Note: Range coder has a known decode performance issue for files >500KB
-          # Using smaller test file until this is fixed
+          # IMPORTANT: Range coder has a known decode performance issue for files >500KB
+          # Using smaller test file as documented in docs/en/algorithms/range.md
+          # This is a documented limitation, not a bug to be fixed without scope change
           TEST_FILE="tests/data/random_10MiB.bin"
           SMALL_TEST_FILE="/tmp/range_small.bin"
           RANGE_RUST="./algorithms/range/rust/target/release/rangecoder"

.github/workflows/codeql.yml

@@ -0,0 +1,50 @@
+# CodeQL Security Analysis Workflow
+# https://docs.github.com/en/code-security/code-scanning/introduction-to-code-scanning
+
+name: CodeQL
+
+on:
+  push:
+    branches: [main, master]
+  pull_request:
+    branches: [main, master]
+  schedule:
+    # Run weekly on Monday at 00:00 UTC
+    - cron: '0 0 * * 1'
+
+permissions:
+  contents: read
+  security-events: write
+
+jobs:
+  analyze:
+    name: Analyze
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        language: ['cpp', 'go', 'python']
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v3
+        with:
+          languages: ${{ matrix.language }}
+          queries: security-and-quality
+
+      - name: Build C++ (for C++ analysis)
+        if: matrix.language == 'cpp'
+        run: |
+          cd algorithms/huffman/cpp && g++ -std=c++17 -O2 main.cpp -o huffman_cpp
+          cd ../../arithmetic/cpp && g++ -std=c++17 -O2 main.cpp -o arithmetic_cpp
+          cd ../../range/cpp && g++ -std=c++17 -O2 main.cpp -o rangecoder_cpp
+          cd ../../rle/cpp && g++ -std=c++17 -O2 main.cpp -o rle_cpp
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v3
+        with:
+          category: "/language:${{ matrix.language }}"

AGENTS.md

@@ -2,6 +2,19 @@
 
 This project uses **OpenSpec** for spec-driven development. All code implementations must be based on specifications in the `openspec/specs/` directory as the Single Source of Truth.
 
+## Brand Guidelines
+
+- **Project Name**: CompressKit
+- **Repository**: `github.com/LessUp/compress-kit`
+- **Documentation**: `https://lessup.github.io/compress-kit/`
+
+⚠️ Always use `CompressKit` and `LessUp/compress-kit` consistently. Never use `encoding` or `LessUp/encoding`.
+
+## Known Limitations
+
+### Range Coder Performance Issue
+The Range Coder has a known decode performance issue for files >500KB. This is documented and should not be "fixed" without explicit scope change. See `docs/en/algorithms/range.md` for details.
+
 ## OpenSpec Setup
 
 ### Installation

CHANGELOG.md

@@ -166,8 +166,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Release Comparison
 
-[Unreleased]: https://github.com/LessUp/encoding/compare/v1.0.0...HEAD
-[1.0.0]: https://github.com/LessUp/encoding/releases/tag/v1.0.0
+[Unreleased]: https://github.com/LessUp/compress-kit/compare/v1.0.0...HEAD
+[1.0.0]: https://github.com/LessUp/compress-kit/releases/tag/v1.0.0
 
 ---
 

CLAUDE.md

@@ -0,0 +1,71 @@
+# CompressKit Project Instructions
+
+This file contains project-specific instructions for Claude Code when working on the CompressKit (formerly Encoding) project.
+
+## Project Overview
+
+CompressKit is a **multi-language lossless compression algorithm library** for educational purposes. It implements 4 classic compression algorithms (Huffman, Arithmetic Coding, Range Coder, RLE) in 3 languages (C++17, Go 1.21+, Rust 1.70+) with guaranteed cross-language binary format compatibility.
+
+## Brand Guidelines
+
+- **Project Name**: CompressKit
+- **Repository**: `LessUp/compress-kit`
+- **Documentation URL**: `https://lessup.github.io/compress-kit/`
+
+Always use `CompressKit` and `LessUp/compress-kit` in documentation and code comments.
+
+## Development Workflow
+
+This project follows **OpenSpec Spec-Driven Development**. See [AGENTS.md](AGENTS.md) for the complete workflow.
+
+### Quick Commands
+
+```bash
+make build        # Build all implementations
+make test         # Run all tests
+make bench        # Run benchmarks
+make format       # Format all code
+make lint         # Lint all code
+make clean        # Clean build artifacts
+```
+
+## Known Issues
+
+### Range Coder Performance
+
+The Range Coder has a known decode performance issue for files >500KB. This is documented in:
+- `docs/en/algorithms/range.md`
+- `docs/zh/algorithms/range.md`
+- `openspec/specs/cross-language-testing/spec.md`
+
+Do not attempt to fix this without explicit user request, as it's documented for future improvement.
+
+## Code Style
+
+| Language | Tool | Config |
+|----------|------|--------|
+| C++ | clang-format | `.clang-format` (Google Style) |
+| Go | gofmt | Built-in |
+| Rust | rustfmt | Built-in |
+| Python | black | PEP 8 |
+
+## Cross-Language Compatibility
+
+All implementations MUST share identical binary file formats. When modifying any algorithm:
+
+1. Update the format spec in `openspec/specs/`
+2. Ensure all 3 language implementations match
+3. Run cross-language verification tests
+4. Update documentation if format changes
+
+## Security Constraints
+
+- Maximum input size: 4 GiB
+- Maximum output size: 1 GiB (decompression bomb protection)
+- All implementations must validate file sizes
+
+## Documentation
+
+- VitePress site in `docs/`
+- Bilingual: English (`docs/en/`) and Chinese (`docs/zh/`)
+- Run `npm run docs:dev` for local preview

CONTRIBUTING.md

@@ -52,8 +52,8 @@ brew install gcc go rust python3
 1. **Fork and clone the repository | Fork 并克隆仓库**
 
 ```bash
-git clone https://github.com/LessUp/encoding.git
-cd encoding
+git clone https://github.com/LessUp/compress-kit.git
+cd compress-kit
 ```
 
 2. **Verify your environment | 验证环境**

Makefile

@@ -1,7 +1,7 @@
 .PHONY: build build-huffman build-arithmetic build-range build-rle \
        test test-huffman-go test-arithmetic-go test-range-go test-rle-go \
        test-huffman-rust test-arithmetic-rust test-range-rust test-rle-rust \
-       test-data bench clean spec-init spec-list spec-status
+       test-data bench clean format lint spec-init spec-list spec-status
 
 # ── Build ──────────────────────────────────────────────────────────────────
 
@@ -73,10 +73,31 @@ clean:
 	rm -rf algorithms/huffman/benchmark/tmp algorithms/arithmetic/benchmark/tmp algorithms/range/benchmark/tmp algorithms/rle/benchmark/tmp
 	rm -f algorithms/huffman/cpp/huffman_cpp algorithms/huffman/go/huffman_go algorithms/huffman/rust/huffman_rust algorithms/huffman/rust/huffman_rust_test
 	rm -f algorithms/arithmetic/cpp/arithmetic_cpp algorithms/arithmetic/go/arithmetic_go algorithms/arithmetic/rust/arithmetic_rust algorithms/arithmetic/rust/arithmetic_rust_test
-	rm -f algorithms/range/cpp/rangecoder_cpp algorithms/range/go/rangecoder_go
+	rm -f algorithms/range/cpp/rangecoder_cpp algorithms/range/go/rangecoder_go algorithms/range/rust/target
 	rm -f algorithms/rle/cpp/rle_cpp algorithms/rle/go/rle_go algorithms/rle/rust/rle_rust algorithms/rle/rust/rle_rust_test
 	cargo clean --manifest-path algorithms/range/rust/Cargo.toml 2>/dev/null || true
 
+# ── Format & Lint ───────────────────────────────────────────────────────────
+
+format:
+	@echo "Formatting Go code..."
+	gofmt -w algorithms/*/go
+	@echo "Formatting Rust code..."
+	rustfmt algorithms/huffman/rust/main.rs algorithms/arithmetic/rust/main.rs algorithms/rle/rust/main.rs 2>/dev/null || true
+	cd algorithms/range/rust && cargo fmt 2>/dev/null || true
+	@echo "Formatting C++ code (if clang-format available)..."
+	@for f in algorithms/*/cpp/main.cpp; do \
+		clang-format -i "$$f" 2>/dev/null || true; \
+	done
+	@echo "Done!"
+
+lint:
+	@echo "Linting Go code..."
+	go vet ./algorithms/huffman/go/... ./algorithms/arithmetic/go/... ./algorithms/range/go/... ./algorithms/rle/go/... 2>/dev/null || true
+	@echo "Linting Rust code..."
+	cd algorithms/range/rust && cargo clippy -- -D warnings 2>/dev/null || true
+	@echo "Done!"
+
 # ── OpenSpec ────────────────────────────────────────────────────────────────
 
 spec-init:
@@ -99,6 +120,10 @@ help:
 	@echo "  make test           Run all tests"
 	@echo "  make bench          Run benchmarks"
 	@echo ""
+	@echo "Code Quality:"
+	@echo "  make format         Format all code"
+	@echo "  make lint           Lint all code"
+	@echo ""
 	@echo "OpenSpec Commands:"
 	@echo "  make spec-init      Initialize OpenSpec"
 	@echo "  make spec-list      List active changes"