Completeness sweep: 20 new pages (Coin Change, House Robber, Kadane, LIS, Merge Sorted Array, Set Matrix Zeroes, Add Two Numbers, Diameter, Network Delay, Word Ladder II, Rotting Oranges, Longest Valid Parentheses, Valid Palindrome, First Missing Positive, Subarray Sums Div By K, Arrows, Permutations II, Walls And Gates, LRU 7-variants) + auto-generated Repo Coverage Index mapping all 667 files + roadmap appendix · arpanpathak/AdvancedAlgorithmPatterns@361a53c