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>

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