Add CONTRIBUTING.md and GitHub Pages landing page

- CONTRIBUTING.md: build from source, run tests, PR guidelines, language fix workflow
- docs/index.html: SEO-optimized landing page with benchmark data, feature grid, comparison table

Author: DeusData

CONTRIBUTING.md

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+# Contributing to codebase-memory-mcp
+
+Contributions are welcome. This guide covers setup, testing, and PR guidelines.
+
+## Build from Source
+
+**Prerequisites**: Go 1.26+, a C compiler (gcc or clang — needed for tree-sitter CGO bindings), Git.
+
+```bash
+git clone https://github.com/DeusData/codebase-memory-mcp.git
+cd codebase-memory-mcp
+CGO_ENABLED=1 go build -o codebase-memory-mcp ./cmd/codebase-memory-mcp/
+```
+
+macOS: `xcode-select --install` provides clang.
+Linux: `sudo apt install build-essential` (Debian/Ubuntu) or `sudo dnf install gcc` (Fedora).
+
+## Run Tests
+
+```bash
+go test ./... -count=1
+```
+
+Key test files:
+- `internal/pipeline/langparity_test.go` — 125+ language parity cases
+- `internal/pipeline/astdump_test.go` — 90+ AST structure cases
+- `internal/pipeline/pipeline_test.go` — integration tests
+
+## Run Linter
+
+```bash
+golangci-lint run ./...
+```
+
+## Project Structure
+
+```
+cmd/codebase-memory-mcp/  Entry point (MCP server + CLI + install/update)
+internal/
+  lang/                   Language specs (35 languages, tree-sitter node types)
+  parser/                 Tree-sitter grammar loading
+  pipeline/               Multi-pass indexing pipeline
+  httplink/               Cross-service HTTP route matching
+  cypher/                 Cypher query engine
+  store/                  SQLite graph storage
+  tools/                  MCP tool handlers (12 tools)
+  watcher/                Background auto-sync
+  discover/               File discovery with .cgrignore
+  fqn/                    Qualified name computation
+```
+
+## Adding or Fixing Language Support
+
+Most language issues are in `internal/lang/<name>.go` (node type configuration) or `internal/pipeline/` (extraction logic).
+
+**Workflow for language fixes:**
+
+1. Find the relevant language spec in `internal/lang/`
+2. Use AST dump tests to see actual tree-sitter node types:
+   ```bash
+   go test ./internal/pipeline/ -run TestASTDump -v
+   ```
+3. Compare configured node types vs actual AST output
+4. Update the language spec and add/fix parity test cases
+5. Verify with a real open-source repo (see `BENCHMARK_REPORT.md` for test repos per language)
+
+## Pull Request Guidelines
+
+- One logical change per PR
+- Include tests for new functionality
+- Run `go test ./... -count=1` and `golangci-lint run` before submitting
+- Keep PRs focused — avoid unrelated reformatting or refactoring
+- Reference the issue number in your PR description
+
+## Good First Issues
+
+Check [issues labeled `good first issue`](https://github.com/DeusData/codebase-memory-mcp/labels/good%20first%20issue) for beginner-friendly tasks with clear scope and guidance.
+
+## License
+
+By contributing, you agree that your contributions will be licensed under the MIT License.