docs: Add YAML front matter to all documentation files

**Purpose:** Prepare documentation for publishing as blog posts or book

**YAML Headers Include:**
- title: Document title
- subtitle: Optional subtitle for context
- description: Brief summary for SEO/indexing
- date: Creation date
- updated: Last update date (for status docs)
- author: Jukka Aho
- categories: Taxonomic classification
- keywords: Search/indexing keywords
- audience: Target reader (users/contributors/researchers)
- level: Difficulty level (beginner/intermediate/advanced/expert)
- type: Document type (manual/guide/theory/benchmark/status)
- series: Which manual it belongs to
- chapter: Book structure (for The JuliaFEM Book)
- status: Current state (completed/work in progress/active maintenance)
- math: Whether document contains mathematical notation
- prerequisites: Required background knowledge
- tools: Software/packages used (for benchmarks)
- context: Background information

**Files Updated:**
- docs/README.md (main index)
- docs/user/README.md (user manual index)
- docs/contributor/README.md (contributor manual index)
- docs/book/README.md (book index)
- docs/contributor/testing_philosophy.md
- docs/contributor/status.md
- docs/contributor/test_fixes_needed.md
- docs/book/lagrange_basis_functions.md
- docs/book/benchmarks/shape_function_derivatives_ad_vs_manual.md
- scripts/README.md

**Benefits:**
- Ready for static site generators (Jekyll, Hugo, MkDocs)
- Can generate book with proper metadata
- SEO-friendly with descriptions and keywords
- Clear audience/level targeting
- Trackable with dates and status
- Organized by series and chapters

**Compatible With:**
- Jekyll (GitHub Pages)
- Hugo (fast static site generator)
- MkDocs (Python-based documentation)
- Jupyter Book (interactive books)
- Docusaurus (React-based docs)
- Custom publishing scripts

docs/README.md

@@ -1,3 +1,13 @@
+---
+title: "JuliaFEM Documentation"
+description: "Three-tier documentation structure for users, contributors, and researchers"
+date: 2025-11-09
+author: "Jukka Aho"
+categories: ["documentation", "guide"]
+keywords: ["juliafem", "finite element", "documentation", "manual"]
+type: "index"
+---
+
 # JuliaFEM Documentation
 
 Welcome! JuliaFEM documentation is organized into **three manuals** for three different audiences:

docs/book/README.md

@@ -1,3 +1,17 @@
+---
+title: "The JuliaFEM Book"
+subtitle: "A comprehensive manual mixing theory, software design, and personal experience"
+description: "Deep dive into FEM theory, design philosophy, and research directions"
+date: 2025-11-09
+author: "Jukka Aho"
+categories: ["theory", "research", "philosophy"]
+keywords: ["fem theory", "contact mechanics", "design philosophy", "research"]
+audience: "researchers and theory enthusiasts"
+level: "expert"
+type: "book"
+status: "work in progress"
+---
+
 # The JuliaFEM Book
 
 **Audience:** Advanced researchers, theory nerds, those who want to understand the "why" and "how" at a deep level. And Jukka.

docs/book/benchmarks/shape_function_derivatives_ad_vs_manual.md

@@ -1,3 +1,22 @@
+---
+title: "Shape Function Derivatives: Hand-Calculated vs Automatic Differentiation"
+subtitle: "Performance benchmark for Tet10 element derivatives"
+description: "Comprehensive benchmark showing 30× performance difference between manual and AD derivatives"
+date: 2025-11-09
+author: "Jukka Aho"
+categories: ["benchmarks", "performance", "research"]
+keywords: ["automatic differentiation", "performance", "shape functions", "derivatives", "tensors.jl", "tet10"]
+audience: "developers and researchers"
+level: "advanced"
+type: "benchmark"
+series: "The JuliaFEM Book"
+chapter: "Part IV: Research"
+experiment_date: "2025-11-09"
+tools: ["BenchmarkTools.jl", "Tensors.jl"]
+status: "completed"
+context: "Major zero-allocation refactoring (immutable Element, tuple-based APIs)"
+---
+
 # Shape Function Derivatives: Hand-Calculated vs Automatic Differentiation
 
 **Date:** November 9, 2025  

docs/book/lagrange_basis_functions.md

@@ -1,3 +1,20 @@
+---
+title: "Lagrange Basis Functions"
+subtitle: "Mathematical foundations of finite element interpolation"
+description: "Complete derivation of Lagrange basis functions using Vandermonde matrix method"
+date: 2025-11-09
+author: "Jukka Aho"
+categories: ["theory", "mathematics", "fem"]
+keywords: ["lagrange basis", "shape functions", "interpolation", "vandermonde matrix", "fem theory"]
+audience: "researchers and advanced users"
+level: "expert"
+type: "theory"
+series: "The JuliaFEM Book"
+chapter: "Part I: Foundations"
+math: true
+prerequisites: ["linear algebra", "numerical analysis", "fem basics"]
+---
+
 # Lagrange Basis Functions in JuliaFEM
 
 **Date:** November 9, 2025  

docs/contributor/README.md

@@ -1,3 +1,15 @@
+---
+title: "JuliaFEM Contributor Manual"
+description: "Technical guide for developers and contributors"
+date: 2025-11-09
+author: "Jukka Aho"
+categories: ["development", "contributor guide"]
+keywords: ["juliafem", "development", "architecture", "testing", "performance"]
+audience: "developers"
+level: "advanced"
+type: "manual"
+---
+
 # JuliaFEM Contributor Manual
 
 **Audience:** Developers, contributors, advanced users who want to extend or modify JuliaFEM.

docs/contributor/status.md

@@ -1,4 +1,18 @@
-# JuliaFEM Revival Status - November 8, 2025
+---
+title: "JuliaFEM Project Status"
+description: "Current state of the revival project as of November 2025"
+date: 2025-11-08
+updated: 2025-11-08
+author: "Jukka Aho"
+categories: ["status", "progress"]
+keywords: ["status", "progress", "revival", "roadmap"]
+audience: "contributors"
+level: "intermediate"
+type: "status report"
+series: "Contributor Manual"
+---
+
+# JuliaFEM Status
 
 ## ✅ SUCCESS: Package Loads!
 

docs/contributor/test_fixes_needed.md

@@ -1,3 +1,18 @@
+---
+title: "Test Fixes Needed"
+description: "Known test failures and fixes required for full test suite passing"
+date: 2025-11-09
+updated: 2025-11-09
+author: "Jukka Aho"
+categories: ["testing", "todo"]
+keywords: ["tests", "failures", "fixes", "todo"]
+audience: "contributors"
+level: "intermediate"
+type: "technical note"
+series: "Contributor Manual"
+status: "active maintenance"
+---
+
 # Test Fixes Needed
 
 **Date:** November 8, 2025  

docs/contributor/testing_philosophy.md

@@ -1,4 +1,17 @@
-# JuliaFEM Testing Philosophy
+---
+title: "Testing Philosophy"
+description: "How and why we test in JuliaFEM"
+date: 2025-11-08
+author: "Jukka Aho"
+categories: ["testing", "quality assurance"]
+keywords: ["testing", "unit tests", "verification", "validation"]
+audience: "contributors"
+level: "intermediate"
+type: "guide"
+series: "Contributor Manual"
+---
+
+# Testing Philosophy
 
 **Date:** November 9, 2025  
 **Goal:** 99% code coverage with educational, fast, well-structured tests  

docs/user/README.md

@@ -1,3 +1,15 @@
+---
+title: "JuliaFEM User Manual"
+description: "Quick start guide and practical tutorials for end users"
+date: 2025-11-09
+author: "Jukka Aho"
+categories: ["user guide", "tutorial"]
+keywords: ["juliafem", "quick start", "tutorial", "examples"]
+audience: "end users"
+level: "beginner"
+type: "manual"
+---
+
 # JuliaFEM User Manual
 
 **Audience:** End users, engineers, students who want to run simulations and get results.

scripts/README.md

@@ -1,3 +1,15 @@
+---
+title: "JuliaFEM Scripts"
+description: "Development and code generation scripts for JuliaFEM"
+date: 2025-11-09
+author: "Jukka Aho"
+categories: ["development", "tools", "automation"]
+keywords: ["scripts", "code generation", "automation", "development tools"]
+audience: "contributors"
+level: "intermediate"
+type: "technical documentation"
+---
+
 # JuliaFEM Scripts
 
 This directory contains development and code generation scripts for JuliaFEM.