Prepare 1.5.0 release

[jeffpaul]

Replaces @since n.e.x.t tags with @since 1.5.0 and bumps the AiClient::VERSION constant to 1.5.0.

👨‍💻 Generated by me, no AI.

Closes #284.

[github-actions]

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Co-authored-by: jeffpaul <jeffpaul@git.wordpress.org>
Co-authored-by: dkotter <dkotter@git.wordpress.org>
Co-authored-by: JasonTheAdams <jason_the_adams@git.wordpress.org>

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.58%. Comparing base (a164848) to head (17eb7b1).

Additional details and impacted files

@@            Coverage Diff            @@
##              trunk     #294   +/-   ##
=========================================
  Coverage     86.58%   86.58%           
  Complexity     1383     1383           
=========================================
  Files            69       69           
  Lines          4449     4449           
=========================================
  Hits           3852     3852           
  Misses          597      597           

Flag	Coverage Δ
unit	86.58% <ø> (ø)

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