fix: clamp seekable end to start instead of 0

[alex-barstow]

Description

We clamped the calculated seekable end (the true seekable end minus the liveEdgeDelay) to 0 instead of the seekable start, which resulted in the possibility of having seekable ranges like [5, 0], where the end is less than the start.

Specific Changes proposed

We should clamp the calculated seekable end to the start instead of 0 to prevent this possibility.

Requirements Checklist

• Feature implemented / Bug fixed
• If necessary, more likely in a feature request than a bug fix
  • Unit Tests updated or fixed
  • Docs/guides updated
  • Example created (starter template on JSBin)
• Reviewed by Two Core Contributors

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.96%. Comparing base (fef62d9) to head (8bef6d1).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1564   +/-   ##
=======================================
  Coverage   83.95%   83.96%           
=======================================
  Files          44       44           
  Lines       11683    11681    -2     
  Branches     2612     2611    -1     
=======================================
- Hits         9809     9808    -1     
+ Misses       1874     1873    -1     

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