Fix PDF diagram text rendering with format-optimized generation

Problem: SVG diagrams had missing text in PDFs due to Inkscape conversion
issues with foreignObject elements used by Mermaid for HTML text rendering.

Solution: Implement format-specific optimal generation:
- HTML: SVG files for perfect vector scaling and text rendering
- PDF: High-resolution PNG files (3x scale) for sharp images with readable text

Changes:
- Generate SVG for HTML output using standard mmdc command
- Generate PNG for PDF output using mmdc with --scale 3 for high resolution
- Remove SVG LaTeX package dependency and Inkscape requirement
- Update documentation to reflect the dual-format approach

Results:
- HTML: Crisp, scalable vector diagrams with perfect text
- PDF: Sharp, high-resolution raster diagrams with clear text
- No external dependencies beyond mermaid-cli

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

CLAUDE.md

@@ -42,7 +42,7 @@ cabal repl
 The application consists of:
 
 1. **Main.hs** (app/Main.hs:1-69) - Entry point and core logic
-   - `processMermaid` (app/Main.hs:21-34) - Transforms Mermaid code blocks into SVG images
+   - `processMermaidBlock` (app/Main.hs:54-79) - Transforms Mermaid code blocks into images (SVG for HTML, high-res PNG for PDF)
    - `transformDoc` (app/Main.hs:36-37) - Walks the Pandoc AST to process all blocks
    - `compileToPDF` (app/Main.hs:47-58) - Converts Markdown to PDF using LaTeX
    - `compileToHTML` (app/Main.hs:60-68) - Converts Markdown to HTML
@@ -50,7 +50,7 @@ The application consists of:
 The tool uses Pandoc's AST transformation capabilities to:
 1. Parse Markdown input
 2. Find Mermaid code blocks
-3. Generate SVG files using mermaid-cli (mmdc)
+3. Generate image files using mermaid-cli (mmdc) - SVG for HTML, high-resolution PNG for PDF
 4. Replace code blocks with image references
 5. Output final PDF/HTML
 
@@ -59,7 +59,7 @@ The tool uses Pandoc's AST transformation capabilities to:
 External requirements:
 - GHC 9.12.2 and Cabal 3.16 (install via ghcup)
 - Pandoc library
-- TeX Live (for PDF generation via pdflatex)
+- TeX Live (for PDF generation via XeLaTeX)
 - Mermaid CLI (`npm install -g @mermaid-js/mermaid-cli`)
 
 To install GHC and Cabal:

app/Main.hs

@@ -58,19 +58,23 @@ processMermaidBlock (SourceDir sourceDir) (OutputPath outputPath) (CodeBlock (id
       let DiagramId diagId = generateDiagramId id' contents
           diagIdStr = T.unpack diagId
           mmdFile = sourceDir </> diagIdStr <> ".mmd"
-          pngFile = sourceDir </> diagIdStr <> ".png"
-          -- Determine the correct image path based on output format
-          imagePath = if isHTMLOutput outputPath 
-                      then takeFileName pngFile  -- Just filename for HTML
-                      else pngFile               -- Full path for PDF/LaTeX
+          -- Use SVG for HTML (scalable), high-res PNG for PDF (text compatibility)
+          (outputFile, imagePath) = if isHTMLOutput outputPath
+                                   then let svgFile = sourceDir </> diagIdStr <> ".svg"
+                                        in (svgFile, takeFileName svgFile)
+                                   else let pngFile = sourceDir </> diagIdStr <> ".png"
+                                        in (pngFile, pngFile)
 
       -- Use bracket to ensure cleanup of temporary mermaid file
       bracket
         (TIO.writeFile mmdFile contents >> return mmdFile)
         (\file -> removeFile file `catch` \(_ :: SomeException) -> return ())
         (\_ -> do
-          void $ callProcess mermaidCommand ["-i", mmdFile, "-o", pngFile]
-          putStrLn $ successEmoji <> " Generated " <> pngFile
+          -- Generate with appropriate format and quality for output type
+          if isHTMLOutput outputPath
+            then void $ callProcess mermaidCommand ["-i", mmdFile, "-o", outputFile]
+            else void $ callProcess mermaidCommand ["-i", mmdFile, "-o", outputFile, "--scale", "3"]
+          putStrLn $ successEmoji <> " Generated " <> outputFile
           return $ Para [Image nullAttr [] (T.pack imagePath, "Mermaid diagram")])
 processMermaidBlock _ _ block = return block