ai/live: Retry ffmpeg more often.

[j0sh]

Instead of quitting on error, retry. Clean exits are rare; we almost always get an error.

Check for context cancellation which indicates a swap or disconnect. Quit on those. We already
check for disconnected input after the sleep.

This helps fix the case where the output disconnects but the rest of the processing keeps going.

Also lazily instantiate the output reader per retry, so we aren't blasting out 5+ seconds worth of
buffered data after each retry.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 31.60888%. Comparing base (5d4a57d) to head (1745781).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
server/ai_live_video.go	0.00000%	10 Missing ⚠️

Additional details and impacted files

@@                 Coverage Diff                 @@
##              master       #3708         +/-   ##
===================================================
- Coverage   31.62285%   31.60888%   -0.01397%     
===================================================
  Files            157         157                 
  Lines          47472       47474          +2     
===================================================
- Hits           15012       15006          -6     
- Misses         31566       31573          +7     
- Partials         894         895          +1     

Files with missing lines	Coverage Δ
server/ai_live_video.go	0.00000% <0.00000%> (ø)

... and 3 files with indirect coverage changes

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Files with missing lines	Coverage Δ
server/ai_live_video.go	0.00000% <0.00000%> (ø)

... and 3 files with indirect coverage changes

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