fix(kvb-org-rasci): open the register and its lock without following links

The council root is writable by every agent, and operator.py runs
rasci.database() outside the sandbox. A symlinked rasci.json made it
read any JSON file the operator can read and write it back into the
council as a regular file; a symlinked rasci.lock made it create files
at the link target; a FIFO hung every register call.

load() now reads through nofollow.read_text and database() locks and
writes through nofollow.locked and nofollow.replace. A register that is
no object of task objects, or nested past the recursion limit, exits 2
instead of a traceback. nofollow.open_below also refuses a file with
more than one link, so a hard link to a file outside the council is
refused like a symlink.

🎯 Fix: 96 %
💥 Break: 3 %
💸 Cost: 99 %
⏱️ Time: 95 %
🛡️ Security: 100 %
🏆 Score: 99
🚦 Gate: ✅ 90/5, cost and time <= 100, security 100 %

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_nofollow.py

@@ -100,6 +100,17 @@ class TestNofollow(unittest.TestCase):
                     write(link)
                 self.assertFalse(dangling.exists())
 
+    def test_a_hard_linked_name_is_refused_and_its_target_kept(self):
+        followers = {name: write for name, write in self.writes(self.root).items() if name not in ("replace", "create")}
+        for name, write in followers.items():
+            with self.subTest(write=name):
+                link = self.root / name
+                os.link(self.victim, link)
+                with self.assertRaises(OSError):
+                    write(link)
+                self.assertEqual(self.victim.read_text(encoding="utf-8"), "keep")
+                link.unlink()
+
     def test_a_symlinked_directory_is_refused_and_nothing_lands_in_its_target(self):
         (self.root / "d").symlink_to(self.victims)
         (self.victims / "f").write_text("keep", encoding="utf-8")