reuse_refs_check: sibling repos beside the MAIN clone for a worktree (R-1114)

FELHOM_WORKSPACE (set by felhom-controller's runner) names where the sibling repos are; the worktree's own
main clone is skipped. Unset: unchanged. Test red-proved both ways.

Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

scripts/CHANGELOG.md

@@ -1,3 +1,11 @@
+## 2026-10-17 — reuse_refs_check.py: sibling repos beside the MAIN clone, for a worktree (R-1114)
+
+`find_siblings` reads `FELHOM_WORKSPACE` when set — felhom-controller's runner sets it to the main clone's parent
+(`controller/scripts/shared_scripts.py`) — and skips the worktree's own main clone, so a path deleted in the worktree
+never resolves in the main clone. Unset, nothing changes (the other three runners). Test
+`test_worktree_searches_the_workspace_not_its_own_main_clone`, red-proved both ways (no env → the sibling is not found;
+no skip → the main clone is searched).
+
 ## 2026-10-16 — build-hub.sh 1.25.0: a version number is pushed once (R-1098)
 
 `scripts/build-hub.sh` refuses `--push`/`--multiarch` of a tag the registry already has, and refuses when the registry