[4/4] Reduce slow integration test workloads

[jlnav]

• Reduces MFKG to the initial sample plus one acquisition batch while preserving batch and async coverage.
• Reduces variable-resource runs from 40 to 12 requested simulations and directly asserts completion and resource variation.
• Verified both MFKG modes and all four local multiprocessing start-method runs.
• Stack parent: fix mfkg test issue. clarify asking questions in AGENTS.md #1780 -> test-runner/controls-and-timings -> ci/fast-feedback-topology -> ci/integration-tiers-and-shards.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.14%. Comparing base (d6126c8) to head (d0dd321).

Additional details and impacted files

@@                         Coverage Diff                         @@
##           ci/integration-tiers-and-shards    #1781      +/-   ##
===================================================================
+ Coverage                            69.30%   70.14%   +0.83%     
===================================================================
  Files                                   84       84              
  Lines                                 9093     9093              
  Branches                              1402     1402              
===================================================================
+ Hits                                  6302     6378      +76     
+ Misses                                2470     2392      -78     
- Partials                               321      323       +2     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.