Add Job Summary reports to Conformance tests

[enrichman]

The Conformance tests for the shared mode are failing (we know that), but it was hard to see how many of them, and which one.

This PR adds a Job Summary with a markdown table showing which tests are failing:

See run: https://github.com/enrichman/k3k/actions/runs/19249567094

It also drops the job to run the sigs test, that was not really used.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.73%. Comparing base (a84c49f) to head (debf097).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #553      +/-   ##
==========================================
+ Coverage   59.58%   59.73%   +0.15%     
==========================================
  Files          56       56              
  Lines        5151     5151              
==========================================
+ Hits         3069     3077       +8     
+ Misses       1798     1794       -4     
+ Partials      284      280       -4     

Flag	Coverage Δ
cli	53.67% <ø> (+0.54%)	⬆️
controller	58.40% <ø> (-0.06%)	⬇️
e2e	58.40% <ø> (-0.06%)	⬇️
unit	41.57% <ø> (+0.04%)	⬆️

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