fix(content): repair client consumers broken by the Duncarrow purge

The purge plan assumed content/world/** was pure build output. The client
reads it: content_db.gd loads content/world/topics/ (now absent, since every
topic was Duncarrow-generated) and its tests asserted on deleted ids.

- content_db: a missing content dir is an empty dir, not an error (§13)
- test_content_db: repoint at cosmology canon; drop deleted npc.mera-fenn
- test_content_db: assert the no-body-on-client invariant structurally, so it
  cannot pass vacuously when the topic set is empty
- schema.md: finish repointing the worked example onto specimen.md's ids
- restore a local real-bible --check smoke test (was only in CI)
- roadmap: record that generated content has client consumers

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

client/tests/unit/test_content_db.gd

@@ -52,17 +52,25 @@ func test_null_quest_ref_resolves():
 	assert_eq(db.unresolved_refs(o), [])
 
 
-func test_loads_canon_and_topics():
-	assert_true(db.has_canon("town.duncarrow"))
-	assert_true(db.has_canon("place.the-white-antlers"))
-	assert_true(db.has_topic("rumor.travelers-go-missing"))
+func test_loads_canon():
+	assert_true(db.has_canon("faction.the-seven"))
+	assert_true(db.has_canon("person.the-warden"))
+	assert_true(db.has_canon("rule.disposition-ladder"))
 
 
-func test_topic_skeleton_has_no_body():
-	var t: Dictionary = db.topic("secret.crell-runs-slave-trade")
-	assert_false(t.has("body"))  # bodies are server-only
+func test_no_loaded_topic_has_a_body():
+	# Bodies are server-only (secrecy≥1 knowledge routes to content/server/topics,
+	# never the client). Structural, so it stays a real guard even when the
+	# topic set is empty (as it is now — the last authored topics were purged)
+	# and automatically starts testing something the moment a topic exists.
+	# One assertion, always executed (not per-loop-item), so an empty topic
+	# set still exercises the check instead of asserting zero times.
+	var leaked: Array = []
+	for id in db.topics:
+		if db.topics[id].has("body"):
+			leaked.append(id)
+	assert_eq(leaked, [], "topic(s) leaked a body to the client")
 
 
 func test_legacy_npcs_still_load():
 	assert_true(db.has_npc("fenn"))
-	assert_true(db.has_npc("npc.mera-fenn"))