## Summary
**What is the goal of this PR?** Replace the linear scan of
`lookupHtmlEntity` with a simple binary search to improve lookup
performance.
**What changes are included?**
`lib/Epub/Epub/Entities/htmlEntities.cpp`:
- Sorted the `ENTITY_LOOKUP` array.
- Added a compile-time assertion to guarantee the array remains sorted.
- Rewrote `lookupHtmlEntity` to use a binary search.
## Additional Context
Benchmarked on my x64 laptop (probably will be different on RISC-V)
```
=== Benchmark (53 entities x 10000 iterations) ===
Version Total time Avg per lookup
----------------------------------------------
linear 236.97 ms total 447.11 ns/lookup
binary search 22.09 ms total 41.68 ns/lookup
=== Summary ===
Binary search is 10.73x faster than linear scan.
```
This is a simplified alternative to #1180, focused on keeping the
implementation clean, and maintainable.
### AI Usage
Did you use AI tools to help write this code? _**< NO >**_
---------
Co-authored-by: Zach Nelson <zach@zdnelson.com>
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