docs(plugin-sharing): tighten two comments in the membership recompute

Claude-Session: https://claude.ai/code/session_01KqkTQNLcxVc588eZpJmp1r
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude

packages/plugins/plugin-sharing/src/recipient-membership-recompute.test.ts

@@ -186,7 +186,7 @@ async function boot() {
   /** The account ids `userId`'s own read path admits. */
   const readable = async (userId: string): Promise<string[]> => {
     const filter = await sharing.buildReadFilter(OBJECT, member(userId));
-    expect(filter).not.toBeNull(); // a member context never bypasses — else this reads nothing
+    expect(filter).not.toBeNull(); // a member context is always filtered — else this measures nothing
     const rows = (await ql.find(OBJECT, { where: filter as any, context: SYSTEM } as never)) as any[];
     return rows.map((r) => String(r.id)).sort();
   };

packages/plugins/plugin-sharing/src/recipient-membership-recompute.ts

@@ -32,10 +32,8 @@
  * membership table to watch.
  *
  * The position expansion also unions `sys_member.role`, the ADR-0057 D4
- * transition source. The holder check reads it — a user who still holds the
- * position there keeps the rule's grants when an assignment row goes — but its
- * writes are not watched here: its values are the closed set of membership
- * grades (ADR-0108), not business positions.
+ * transition source, and so does the holder check: a user who still holds the
+ * position there keeps the rule's grants when an assignment row goes.
  *
  * ## Cost: scoped to one user and to the rules that name the recipient
  *