update: move issue #317 to DONE after PR #318 merge

Author: krystophny

BACKLOG.md

@@ -10,7 +10,6 @@
 - [ ] #321: Refactor - apply consistent validation pattern to other PDF write functions
 
 ## DOING (Current Work)
-- [ ] #317: Fix GitHub Pages deployment failure - colored_contours PDF runtime crash in pdf_write_color
 
 ## BLOCKED (Infrastructure Issues)
 
@@ -37,6 +36,7 @@
 - Performance impact validation
 
 ## DONE (Completed)
+- [x] #317: Fix GitHub Pages deployment failure - colored_contours PDF runtime crash in pdf_write_color - FIXED: Added robust RGB validation to prevent PDF color crashes, restored visual showcase (PR #318 merged)
 - [x] #312: Legend Demo plots dont show up on github pages - FIXED: GitHub Pages examples not generating due to auto-examples=false in fpm.toml, enabled automatic example discovery (PR #316 merged)  
 - [x] #311: Simple Sine Wave and Gaussian Default plots shows just axes in examples but no content - FIXED: PNG data rendering regression caused by figure initialization resetting plot_count (PR #315 merged)
 - [x] #272: fix: rescue BACKLOG.md commits from main branch protection - RESCUED: Historical PLAY workflow planning commits (c610cce, ad82dbc) documenting issues #262-271 (PR #314 merged)