feat(content): reparent disposition-ladder to mechanics.md; purge Duncarrow

Move rule.disposition-ladder into content/lore/mechanics.md and delete the
Duncarrow scaffolding (source + 23 generated JSON). Remove the redundant
test_duncarrow.py (routing/secrecy already covered by test_emit.py synthetic
fixtures); repoint a cosmetic slug-test id.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HuHRPE7VfppUJEaoGBEUqZ

tools/content_build/tests/test_duncarrow.py

@@ -1,37 +0,0 @@
-"""End-to-end: the real promoted Duncarrow bible builds green and routes the
-Crell secret correctly (body server-only; the id ships in the gate skeleton)."""
-
-import json
-from pathlib import Path
-
-from content_build.__main__ import _load_world, check
-from content_build.emit import build_trees
-
-REPO = Path(__file__).resolve().parents[3]
-LORE = REPO / "content" / "lore"
-WORLD = REPO / "content" / "world"
-SERVER = REPO / "content" / "server"
-
-
-def test_duncarrow_builds_and_check_is_clean():
-    assert check(LORE, WORLD, SERVER) == 0
-
-
-def test_secret_body_is_server_only():
-    client, server = build_trees(_load_world(LORE))
-    assert "topics/crell-runs-slave-trade.json" in server
-    # the secret's descriptive id ships in the gate skeleton (schema property)...
-    npc = client["npcs/mayor-oswin-crell.json"]
-    assert any(k["fact_id"] == "secret.crell-runs-slave-trade"
-               and k["gate"] == "never" for k in npc["knows"])
-    # ...but its BODY never reaches any client artifact
-    blob = json.dumps(client)
-    assert "elf-slaving" not in blob and "sells them into slavery" not in blob
-
-
-def test_mera_never_holds_the_secret():
-    client, _ = build_trees(_load_world(LORE))
-    fenn = client["npcs/mera-fenn.json"]
-    facts = {k["fact_id"] for k in fenn["knows"]}
-    assert "secret.crell-runs-slave-trade" not in facts
-    assert "fact.crells-guard-acts-alone" in facts

tools/content_build/tests/test_model.py

@@ -13,11 +13,11 @@ def _raw(**over) -> RawEntry:
 
 
 def test_namespace_and_slug():
-    e = entry_from_raw(_raw(id="npc.mera-fenn", type="person",
+    e = entry_from_raw(_raw(id="npc.specimen-teague", type="person",
                             start_disposition="cold",
                             knows=[{"fact": "rumor.x", "gate": "warm"}]))
     assert e.namespace == "npc"
-    assert e.slug == "mera-fenn"
+    assert e.slug == "specimen-teague"
 
 
 def test_category_predicates():