fix(docs,tests): correct the pre-push hook claim, a dead link, MCP cleanup

Problem: the README said setup enables "tracked ... OpenGrep pre-push
hooks", but only .githooks/pre-commit is tracked, so fresh clones get no
pre-push hook. docs/research/prior-art.md pointed to prior-art-full.md,
which has never been in the repository. test_mcp_stdio's TempDir
destructor called the throwing remove_all overload; a failure during
unwinding terminates the test binary and leaves .fold-mcp-test-*
directories behind.

Fix: the README names only the tracked pre-commit hook. The pre-push
hook is not committed: it runs `opengrep --config auto`, which needs the
network. The dead reference is removed. TempDir uses the error_code
remove_all overload. It stays under the working directory, because the
MCP server rejects paths outside its workspace root (moving it to
temp_directory_path broke three MCP tests).

Test: mcp_stdio passes.

README.md

@@ -13,8 +13,7 @@ Requires system-installed LLVM/Clang 18+ and `libz3` development
 headers; Conan handles the rest (spdlog, CLI11, nlohmann_json,
 sqlite3, Catch2). **See [BUILD.md](BUILD.md) for per-platform
 apt/brew install lines and a Docker validation harness.** Setup also enables
-the tracked lint pre-commit and OpenGrep pre-push hooks; install
+the tracked lint pre-commit hook (`.githooks/pre-commit`).
-[OpenGrep](https://opengrep.dev/) before pushing.
 
 ## Usage
 

docs/research/prior-art.md

@@ -1,6 +1,6 @@
 # Prior Art (condensed)
 
-Key papers grounding fold's design. Full annotations in `prior-art-full.md`.
+Key papers grounding fold's design.
 
 ## Buffer overflow
 - **Xu et al. (2020)** *ELAID.* doi:10.1186/s42400-020-00058-2 — interprocedural call graph + SMT on Juliet sinks.

tests/integration/test_mcp_stdio.cpp

@@ -57,13 +57,19 @@ struct TempDir {
     std::filesystem::path path;
 
     TempDir()
+        // Must stay under the working directory: the MCP server rejects paths
+        // outside its workspace root.
         : path(std::filesystem::current_path() /
                (".fold-mcp-test-" +
                 std::to_string(std::chrono::steady_clock::now().time_since_epoch().count()))) {
         std::filesystem::create_directories(path);
     }
 
-    ~TempDir() { std::filesystem::remove_all(path); }
+    // Non-throwing: a destructor that throws during unwinding terminates.
+    ~TempDir() {
+        std::error_code ec;
+        std::filesystem::remove_all(path, ec);
+    }
 };
 
 void writeFile(const std::filesystem::path& path, const std::string& content) {