docs(rules): give each C# rule statement one authoritative file

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

shared/rules/csharp/references/testing-and-dependencies.md

@@ -5,6 +5,5 @@ Apply these rules when changing tests, package references, analyzers, or build d
 * Write deterministic behavior-based tests. Avoid coupling assertions to private call order, implementation details, current time, or uncontrolled external services.
 * Make code testable through clear contracts and dependencies; do not add production hooks or abstractions solely for tests without a concrete need.
 * Prefer the .NET BCL and existing supported packages over new libraries when they solve the problem adequately.
-* Keep dependencies minimal, maintained, compatible, and updated through the repository's normal package-management process.
 * Treat compiler, analyzer, and nullable warnings seriously. Suppress a diagnostic only for a specific, documented reason and narrow the suppression to the affected code.
-* Run focused tests and analyzers for the changed path; broaden verification when shared behavior or compatibility could be affected.
+* Include analyzers in the verification of the changed path.