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/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