ci-health-check: complete dynamic repo discovery (PRI-331)

PR #115's first commit landed dynamic discovery via gh api but missed
three of the five issue requirements. This commit completes them:

- Move headlamp- prefix filtering into jq via startswith() and add
  explicit exclusion for headlamp-agent-skills (skills bundle, not a
  plugin), instead of relying on grep -E '^headlamp-.+'.
- Add PLUGIN_REPOS_FALLBACK with the previously hardcoded list and
  use it when discovery returns empty, instead of exiting with error.
- Add header comment documenting the discovery filter and the
  headlamp-agent-skills exclusion.

Verified jq filter against live API: returns 8 plugin repos, all
prefixed headlamp-, headlamp-agent-skills correctly excluded.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.github/scripts/ci-health-check.sh

@@ -2,19 +2,41 @@
 # ci-health-check.sh — Scan all privilegedescalation repos for CI/CD health
 # Run from: /paperclip/privilegedescalation/engineering/hugh
 # Requires: GH_TOKEN set (use: export GH_TOKEN=$(bash ./get-github-token.sh))
+#
+# Plugin repo discovery
+# ---------------------
+# PLUGIN_REPOS is populated dynamically from the GitHub org so newly created
+# plugin repos are picked up automatically. The filter is:
+#   - non-archived, public repos in the privilegedescalation org
+#   - name starts with "headlamp-"
+#   - excludes "headlamp-agent-skills" (skills bundle, not a Headlamp plugin)
+# If discovery fails (network error, GH_TOKEN missing, API outage), we fall
+# back to a hardcoded list so the health check still produces a useful report.
 set -euo pipefail
 
 ORG="privilegedescalation"
 
+# Hardcoded fallback — kept in sync manually as a safety net for discovery failures.
+PLUGIN_REPOS_FALLBACK=(
+  headlamp-polaris-plugin
+  headlamp-rook-plugin
+  headlamp-sealed-secrets-plugin
+  headlamp-intel-gpu-plugin
+  headlamp-tns-csi-plugin
+  headlamp-kube-vip-plugin
+  headlamp-plugin-template
+  headlamp-argocd-plugin
+)
+
 mapfile -t PLUGIN_REPOS < <(
   gh api --paginate "orgs/${ORG}/repos" \
-    --jq '.[] | select(.archived == false and .visibility == "public") | .name' \
-    2>/dev/null | grep -E '^headlamp-.+' | sort
+    --jq '.[] | select(.archived == false and .visibility == "public" and (.name | startswith("headlamp-")) and .name != "headlamp-agent-skills") | .name' \
+    2>/dev/null | sort
 )
 
 if [ ${#PLUGIN_REPOS[@]} -eq 0 ]; then
-  echo "ERROR: No repos discovered for ${ORG}" >&2
-  exit 1
+  echo "WARNING: dynamic repo discovery returned no results — using hardcoded fallback" >&2
+  PLUGIN_REPOS=("${PLUGIN_REPOS_FALLBACK[@]}")
 fi
 
 echo "=== CI/CD Health Check — $(date -u '+%Y-%m-%d %H:%M UTC') ==="