--fail-zero respects --delay test registration

[mostafaNazari702]

PR Checklist

• Addresses an existing open issue: fixes 🐛 Bug: --fail-zero always fails the test run when --delay is also used #4950
• That issue was marked as status: accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

So --fail-zero + --delay was incorrectly failing runs with exit code 1 even when tests actually executed fine.

the issue was that Runner captures this.total in the constructor but with --delay the tests dont exist yet at that point and they're only registered later when the user's deferred callback runs. so the runner thinks there are 0 tests the whole time.
then --fail-zero kicks in at the end and says “no tests ran => fail the run” even though tests actually did run.

i chose to, instead of trusting the constructor value, we recompute this.total in prepare() right after the delayed setup has finished and just before execution starts. that way it reflects the real suite (including --grep / --invert filtering).

So basically: we just move the "count the tests" moment to when the tests actually exist.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.90%. Comparing base (6695fba) to head (5e0b880).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5992   +/-   ##
=======================================
  Coverage   80.89%   80.90%           
=======================================
  Files          64       64           
  Lines        4602     4603    +1     
  Branches      976      976           
=======================================
+ Hits         3723     3724    +1     
  Misses        879      879           

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