sed: fix brace quantifier delimiter and {,n} bound edge cases

[sylvestre]

@LoukasPap what do you think ? :)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.12%. Comparing base (d9cd538) to head (90ba2cd).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #463   +/-   ##
=======================================
  Coverage   83.12%   83.12%           
=======================================
  Files          13       13           
  Lines        5895     5885   -10     
  Branches      340      339    -1     
=======================================
- Hits         4900     4892    -8     
+ Misses        992      990    -2     
  Partials        3        3           

Flag	Coverage Δ
macos_latest	83.79% <100.00%> (+<0.01%)	⬆️
ubuntu_latest	83.87% <100.00%> (+<0.01%)	⬆️
windows_latest	0.00% <0.00%> (ø)

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[codspeed-hq]

Merging this PR will degrade performance by 3.4%

❌ 1 regressed benchmark
✅ 10 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	number_fix	574.9 ms	595.2 ms	-3.4%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing sylvestre:fix-brace-quantifier-edge-cases (90ba2cd) with main (d9cd538)}

[LoukasPap]

That's very good! Hadn't thought about simplifying the logic of {,} and {,n}, neither the delimiter case (adding the forgotten test cases was a nice catch too). I think the code is now both smarter and cleaner.

[sylvestre]

thanks