test(agents): the cases the review found

Each fixed finding gets a check that fails without its fix: inline code
and a list item's fence, a section removed from between two paragraphs,
a section before an unclosed fence, a CRLF file, no error when there is
nothing to write, a hard-linked and a read-only AGENTS.md, a dependency
whose project file sits in the consumer's own directory, a test's
dependency, and `test --list`. The read-only case needs an ordinary
user, since root writes through the permission bits, and is skipped
under root.

The merge cases go through a helper that counts a throw as a failure,
so one regression no longer ends the run before the cases after it. A
passing run removes its staged copy, whose builds leave a std PCM per
configuration in a tmpfs.

Reverting the inline-code rule, the own-notes exclusion, the skipping
of tests, the `test --list` guard or the paragraph-preserving removal
each fails its check.

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

tests/DependencyNotes/fixture/app/helper.cpp

@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: LGPL-3.0-only
+// SPDX-FileCopyrightText: Copyright (C) 2026 Catcrafts®
+
+import std;
+import Crafter.Build;
+using namespace Crafter;
+
+// A second project file in app/: a dependency whose AGENTS.consumer.md, by
+// where it sits, is app's own.
+extern "C" Configuration CrafterBuildProject(std::span<const std::string_view>) {
+    Configuration cfg;
+    cfg.path = "./";
+    cfg.name = "helper";
+    cfg.outputName = "helper";
+    cfg.type = ConfigurationType::LibraryStatic;
+    return cfg;
+}