Rename E2E namespace to headlamp-dev; fix RBAC manifest

Per CEO directive on PRI-324: the actual cluster namespace for
shared E2E runs is `headlamp-dev`. References to `privilegedescalation-dev`
in the workflow, scripts, and runner RBAC were stale and prevented the
runner SA from acquiring permissions where they were granted on-cluster.

Also fixes the malformed `e2e-ci-runner-polaris` Role added in 0cd9eb0
which incorrectly carried `subjects:` and `roleRef:` (RoleBinding-only
fields) — kept rules-only on the Role and the binding in the matching
RoleBinding below.

Applies QA nits from PR #123: collapsed MISSING_ROLE/MISSING_ROLEBINDING
into a single MISSING flag in the pre-flight step. Dropped the
non-standard `--quiet` flag on get calls (already redirected to /dev/null).

scripts/teardown-e2e-headlamp.sh

@@ -4,13 +4,13 @@
 # Tears down the dedicated E2E Headlamp instance deployed by deploy-e2e-headlamp.sh.
 #
 # Environment:
-#   E2E_NAMESPACE  — namespace to clean up (default: privilegedescalation-dev)
+#   E2E_NAMESPACE  — namespace to clean up (default: headlamp-dev)
 #   E2E_RELEASE    — release/resource name prefix (default: headlamp-e2e)
 set -euo pipefail
 
 REPO_ROOT="$(cd "$(dirname "$0")/.." && pwd)"
 
-E2E_NAMESPACE="${E2E_NAMESPACE:-privilegedescalation-dev}"
+E2E_NAMESPACE="${E2E_NAMESPACE:-headlamp-dev}"
 E2E_RELEASE="${E2E_RELEASE:-headlamp-e2e}"
 
 echo "=== E2E Headlamp Teardown ==="