Fix O(n²) performance issue with single quote smart quote matching

[dereuromark]

Summary

• Pre-compute all single quote opener/closer matches once per text block instead of re-scanning for each potential opener
• Reduces algorithmic complexity from O(n²) to O(n) for documents with many single quotes

Performance Improvement

Test Case	Before	After	Speedup
500 single quotes	368 ms	4.8 ms	~77x
1000 single quotes	2545 ms	14 ms	~180x
2000 single quotes	N/A	39 ms	linear

The issue was that findMatchingSingleQuoteCloser() was called for each potential opener, and each call scanned the entire remaining text. With many single quotes, this became quadratic.

The fix adds a buildSingleQuoteMatchCache() method that pre-computes all matches in a single pass, then parseSmartQuote() simply looks up the pre-computed result in O(1) time.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.62%. Comparing base (6b165b4) to head (7d04ac0).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #172      +/-   ##
============================================
- Coverage     93.98%   93.62%   -0.37%     
- Complexity     3139     3175      +36     
============================================
  Files            93       93              
  Lines          8017     8076      +59     
============================================
+ Hits           7535     7561      +26     
- Misses          482      515      +33     

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