refactor: Remove dead code and stale references (#2189)

- Drop unnecessary `export` from `createAgents` and `resolveAgent` in
  agent-setup.ts — both are internal helpers only ever called within the
  same module via `createCloudAgents`; no external caller imports them
- Fix misleading relative-path sourcing example in github-auth.sh header
  comment — the shell-script rules ban relative `source ./` paths, and the
  example is updated to show the correct CDN eval pattern
- Bump CLI patch version 0.12.17 → 0.12.18

Co-authored-by: spawn-qa-bot <qa@openrouter.ai>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: L <6723574+louisgv@users.noreply.github.com>

sh/shared/github-auth.sh

@@ -1,14 +1,14 @@
 #!/bin/bash
 # Standalone GitHub auth helper — installs gh CLI and runs OAuth login
-# Sourceable by any agent script, or executable directly via curl|bash
+# Executable directly via curl|bash; also sourceable using the CDN URL with eval.
 #
-# Usage (sourced):
-#   source sh/shared/github-auth.sh
-#   ensure_github_auth
-#
-# Usage (direct):
-#   bash sh/shared/github-auth.sh
+# Usage (via curl|bash — recommended):
+#   curl -fsSL https://openrouter.ai/labs/spawn/shared/github-auth.sh | bash
 #   curl -fsSL https://raw.githubusercontent.com/OpenRouterTeam/spawn/main/sh/shared/github-auth.sh | bash
+#
+# Usage (sourced using absolute path or CDN URL):
+#   eval "$(curl -fsSL https://openrouter.ai/labs/spawn/shared/github-auth.sh)"
+#   ensure_github_auth
 
 # ============================================================
 # Logging helpers