docs: update docs and scripts to work with v0.9.0-rc.1

[krancour]

This PR updates main and the edge docs at https://main.kargo.akuity.io/ in a way that facilitates non-engineers being able to easily test-drive the v0.9.0-rc.1 release candidate just by following the quickstart exactly as it is written.

These changes will outlive their usefulness and should be reverted after we cut the official v0.9.0 release.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 51.04%. Comparing base (15deac7) to head (88b12e4).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2612   +/-   ##
=======================================
  Coverage   51.04%   51.04%           
=======================================
  Files         282      282           
  Lines       21056    21056           
=======================================
  Hits        10748    10748           
  Misses       9635     9635           
  Partials      673      673           

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