fix: make e2e scoping on-by-default so fork PRs benefit

[ashishjain0512]

Summary

Fixes e2e scoping for fork PRs (all external contributor PRs).

GitHub does not expose repository variables (vars.*) to workflows triggered by pull requests from forks. The previous logic required E2E_SCOPE_BY_DIAGRAM == 'true' to enable scoping, which meant every fork PR saw the variable as empty and fell back to the full 5-container suite — defeating the purpose of the scoping optimization from #7619 and #7704.

Change

Flip the flag logic: scoping is now ON by default. The repository variable acts as a kill-switch — set it to 'false' to disable scoping. When the variable is unavailable (fork PRs), the expression evaluates to 'true', preserving scoped runs.

Scenario	vars.E2E_SCOPE_BY_DIAGRAM	Scoping active?
Fork PR	unavailable	✅ Yes (default)
Same-repo PR	'true' (or unset)	✅ Yes
Kill-switch engaged	'false'	❌ No (full suite)

Files changed

• .github/workflows/e2e.yml — Flip the flag check from opt-in (!= 'true') to opt-out (= 'false')

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commit: dc52afc

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 3.31%. Comparing base (36ef39e) to head (dc52afc).

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #7709   +/-   ##
=======================================
  Coverage     3.31%   3.31%           
=======================================
  Files          542     542           
  Lines        57206   57206           
  Branches       840     840           
=======================================
  Hits          1898    1898           
  Misses       55308   55308           

Flag	Coverage Δ
unit	3.31% <ø> (ø)

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Build	Status	Details	Updated (UTC)
default (Inspect)	👍 Changes approved	1 changed	May 5, 2026, 9:16 AM