a91bb0b1b8
Replace O(n²) lookups with O(n) preprocessing: 1. createTocEntry(): Build href->spineIndex map once in beginTocPass() instead of scanning spine file for every TOC entry 2. buildBookBin(): Build spineIndex->tocIndex vector in single pass instead of scanning TOC file for every spine entry For 2768-chapter EPUBs, this reduces: - TOC pass: from ~7.6M file reads to ~5.5K reads - buildBookBin: from ~7.6M file reads to ~5.5K reads Memory impact: ~80KB for href map (acceptable trade-off for 10x+ speedup)