Give bots skills: runbooks they load when a job matches

A skill is a runbook: a name, a unique slug, a one-line description of when
it applies, and the markdown body. A run only ever sees the slug and
description (one load_skill tool carries them), and reads the whole body
only when it calls the tool, so a long runbook costs nothing until needed.

Skills are the third extension kind beside MCP servers and custom tools, on
the same botExtensionsSql path, so per-bot, per-workspace and all-bots
grants work the same way, and attachDefaultExtensions hands an every-bot
skill to new bots. load_skill is a reserved tool name, so a custom tool
cannot shadow it, and a built-in wins a clash.

Managed on Settings > Skills; ExtensionRow links each kind to its own page
and a skill never reports a failure, since nothing connects or runs.

src/pages/admin/settings/(partials)/extension-row.tsx

@@ -11,22 +11,35 @@ type Props = {
 };
 
 /**
- * One MCP server or tool a bot or workspace has, and whether it's working.
+ * The settings page each kind is managed on.
+ */
+const ExtensionHrefs = {
+    mcp: "/admin/settings/mcps",
+    tool: "/admin/settings/tools",
+    skill: "/admin/settings/skills",
+} as const;
+
+/**
+ * One MCP server, tool or skill a bot or workspace has, and whether it's
+ * working. A skill has nothing to connect or run, so it never reports a
+ * failure.
  */
 export default function ExtensionRow({ item, busy, onRemove }: Props) {
     const state = !item.enabled
         ? "Off for every bot"
-        : item.state == "error"
-          ? "Not working"
-          : item.state == "untested"
-            ? "Not checked yet"
-            : "";
+        : item.kind == "skill"
+          ? ""
+          : item.state == "error"
+            ? "Not working"
+            : item.state == "untested"
+              ? "Not checked yet"
+              : "";
 
     return (
         <SettingsListRow
             avatar={<IconTile Icon={extensionIcon({ kind: item.kind })} />}
             title={item.name}
-            href={item.kind == "mcp" ? "/admin/settings/mcps" : "/admin/settings/tools"}
+            href={ExtensionHrefs[item.kind]}
             subtitle={[item.detail, state].filter(Boolean).join(" · ")}
         >
             {onRemove ? (