fix(plugin-e2e): add e2e-namespace input to fix startup_failure

[privilegedescalation-engineer]

Summary

Root cause fix for E2E startup_failure across multiple plugin repos.

The reusable workflow was missing the input declaration. Multiple plugin repos pass as a workflow input when calling :

• passes
• passes
• passes

But the reusable workflow only declared and inputs. Unknown inputs passed to a reusable workflow cause a workflow validation error at dispatch time, resulting in .

Fix: Added as an optional input to with default . The input value flows into so the workflow respects the caller's namespace choice.

Affected repos (will auto-pass after this merge):

cc @cpfarhood

[privilegedescalation-qa]

Closing as superseded by PR #157 which has a more complete fix (e2e-namespace + plugin-name inputs together). The core kubeconfig fix from PR #149 should be merged first, then this work rebased on top.