Custom HTTP tools an administrator defines

A row in custom_tools becomes a ToolDef like any built-in, offered beside
the thirteen. The registry had to stop being an import-time constant for
that: `resolve_tools` now returns the schemas *and* the runners together,
carried to the loop on the ToolContext.

That closes a hole on the way. `run_tool` looked names up in the global
REGISTRY with no reference to what had been offered, so a model naming a
tool its chat was gated out of -- a family switched off, a permission the
reader lacks -- had it run anyway. The resolved set is now authoritative.

Arguments come from a model, so an argument may fill a hole but never move
the target: the scheme and host of a URL template are literal, values are
escaped for where they land, and the origin is pinned afterwards. Every
redirect hop is checked the way services/fetch.py checks one, and the
secret is dropped if a hop leaves the origin it was issued for.

Also fixes the tool-activity block claiming every library tool had
"searched the web", which it has done since the second family landed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/lembas/services/harness.py

@@ -57,16 +57,22 @@ MAX_HARNESS_CHARS = 8000
 MAX_NAMED_DOCUMENTS = 5
 
 
-def _families(tools: list[dict[str, Any]]) -> list[str]:
-    """Which families are represented in an offered tool list, in a fixed order."""
-    from lembas.services.tools import FAMILIES, REGISTRY
+def _families(db: DBSession, tools: list[dict[str, Any]]) -> list[str]:
+    """Which families are represented in an offered tool list, in a fixed order.
 
+    Resolved against the database rather than the import-time registry, because
+    an administrator-defined tool is a row and would otherwise contribute no
+    family at all -- which is to say its guidance would never be admitted.
+    """
+    from lembas.services import tools as tools_service
+
+    book = tools_service.registry(db)
     offered = {
-        REGISTRY[name].family
+        book[name].family
         for tool in tools
-        if (name := (tool.get("function") or {}).get("name")) in REGISTRY
+        if (name := (tool.get("function") or {}).get("name")) in book
     }
-    return [family for family in FAMILIES if family in offered]
+    return [family for family in tools_service.families(db) if family in offered]
 
 
 def _tool_names(tools: list[dict[str, Any]]) -> str:
@@ -109,7 +115,7 @@ def context_variables(
     from lembas.services import tools as tools_service
 
     offered = tools or []
-    families = _families(offered)
+    families = _families(db, offered)
     stamp = datetime.now().astimezone()
 
     values: dict[str, str] = {
@@ -185,7 +191,7 @@ def compose(
     return compose_from(
         db,
         variables=context_variables(db, user, offered, chat),
-        families=_families(offered),
+        families=_families(db, offered),
         has_tools=bool(offered),
     )