chore(rename): railiance-bootstrap → railiance-cluster

Update all operational references to reflect the new repo name per
ADR-003 (OAS S2 Cluster Runtime). Historical text in docs preserved.
Gitea remote URL updated locally (Gitea repo rename is a manual step).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tools/seed_node.sh

@@ -21,7 +21,7 @@
 set -euo pipefail
 
 # --------- defaults & flags ----------
-REPO_DIR="${REPO_DIR:-railiance-bootstrap}"
+REPO_DIR="${REPO_DIR:-railiance-cluster}"
 BRANCH="${BRANCH:-main}"
 META_PATH="${META_PATH:-}"   # optional explicit path to panspermia.json
 QUIET=false