vor: pass VOR_WORLDTREE_KEY through to the container

Adds VOR_WORLDTREE_KEY + VOR_WORLDTREE_BASE + VOR_WORLDTREE_MODEL to vor's
compose environment with sane defaults. Empty key falls back to the
in-process MockWorldtree (the /mockup/ surface returns canned fixtures);
a real key issued by architect routes LLM calls at the demo Saga instance.

Key itself lives in ana-docker:/opt/docker/compose/vor/.env (not in the
repo).

stacks/vor/.env.example

@@ -11,3 +11,17 @@ VOR_BIND=0.0.0.0
 # bind-mounted so they survive `docker compose up --force-recreate`.
 VOR_SESSIONS_DIR=/opt/docker/conf/vor/sessions
 VOR_RESPONSES_DIR=/opt/docker/conf/vor/responses
+
+# Worldtree integration — bearer token for the demo Saga instance.
+# Dev-tier Heimdall key, scoped `instantiate:saga`. Without this, the
+# /mockup/ surface falls back to an in-process MockWorldtree (canned
+# fixtures) — boot log shows `WT: in-process mock (...)` instead of
+# `WT: real Worldtree at ...`. The legacy / + /api/sessions endpoints
+# work either way. Issued by architect; rotatable.
+VOR_WORLDTREE_KEY=
+
+# Worldtree instance — defaults to the v1 demo Saga.
+VOR_WORLDTREE_BASE=http://10.250.50.152:8080
+
+# Worldtree model — v1 default.
+VOR_WORLDTREE_MODEL=qwen3.6-35-a3b-heretic