Lint clean up (#64)

Beman Standard lint fixes, split out from the accidentally-bundled #63
(which came off my fork's `main` and picked up unrelated paper work).

Four commits, touching only lint concerns:
- **Rename negative-compile tests to `*.test.cpp`** — [file.test_names]
requires test sources to match `*.test.cpp`; renames the 56
`add_fail_test` sources and updates their CMakeLists references.
- **Add missing SPDX-License-Identifier headers** — [file.license_id]
requires an SPDX header in the first 25 lines; adds Apache-2.0 WITH
LLVM-exception to CMake toolchain files, GitHub workflow/dependabot
configs, and remaining example/paper sources.
- **Link the README library-status badge** — [readme.badges] requires
the badge wrapped in a link to the maturity-model doc.
- **Fix codespell failures in papers/wg21-latex** — real typos fixed;
`FitH` and `ist` added to the ignore list as legitimate technical
tokens.

Author: steve-downey

.github/dependabot.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 # To get started with Dependabot version updates, you'll need to specify which
 # package ecosystems to update and where the package manifests are located.
 # Please see the documentation for all configuration options:

.github/workflows/codeql.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 ---
 # For most projects, this workflow file will not need changing; you simply need
 # to commit it to your repository.

.github/workflows/doxygen-gh-pages.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 name: Doxygen GitHub Pages Deploy Action
 
 on:

.github/workflows/ossf-scorecard-analysis.yml

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 name: Scorecard analysis workflow
 on:
   push:

README.md

@@ -5,7 +5,7 @@ SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 -->
 
 <!-- markdownlint-disable-next-line line-length -->
-![Library Status](https://raw.githubusercontent.com/bemanproject/beman/refs/heads/main/images/badges/beman_badge-beman_library_under_development.svg) ![Continuous Integration Tests](https://github.com/steve-downey/sandbox-expected/actions/workflows/ci_tests.yml/badge.svg) ![Lint Check (pre-commit)](https://github.com/steve-downey/sandbox-expected/actions/workflows/pre-commit-check.yml/badge.svg) [![Coverage](https://coveralls.io/repos/github/steve-downey/sandbox-expected/badge.svg?branch=main)](https://coveralls.io/github/steve-downey/sandbox-expected?branch=main) ![Standard Target](https://github.com/bemanproject/beman/blob/main/images/badges/cpp29.svg)
+[![Library Status](https://raw.githubusercontent.com/bemanproject/beman/refs/heads/main/images/badges/beman_badge-beman_library_under_development.svg)](https://github.com/bemanproject/beman/blob/main/docs/beman_library_maturity_model.md#the-beman-library-maturity-model) ![Continuous Integration Tests](https://github.com/steve-downey/sandbox-expected/actions/workflows/ci_tests.yml/badge.svg) ![Lint Check (pre-commit)](https://github.com/steve-downey/sandbox-expected/actions/workflows/pre-commit-check.yml/badge.svg) [![Coverage](https://coveralls.io/repos/github/steve-downey/sandbox-expected/badge.svg?branch=main)](https://coveralls.io/github/steve-downey/sandbox-expected?branch=main) ![Standard Target](https://github.com/bemanproject/beman/blob/main/images/badges/cpp29.svg)
 
 `beman.expected` is a C++ library implementing the std::expected specification conforming to [The Beman Standard](https://github.com/bemanproject/beman/blob/main/docs/beman_standard.md).
 

cmake/ci-clang-toolchain.cmake

@@ -1,3 +1,6 @@
+# cmake/ci-clang-toolchain.cmake                              -*-cmake-*-
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
 include_guard(GLOBAL)
 
 set(CMAKE_C_COMPILER clang)

cmake/clang-16-toolchain.cmake

@@ -1,3 +1,6 @@
+# cmake/clang-16-toolchain.cmake                              -*-cmake-*-
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
 include_guard(GLOBAL)
 
 set(CMAKE_C_COMPILER clang-16)

cmake/clang-17-toolchain.cmake

@@ -1,3 +1,6 @@
+# cmake/clang-17-toolchain.cmake                              -*-cmake-*-
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
 include_guard(GLOBAL)
 
 set(CMAKE_C_COMPILER clang-17)

cmake/clang-18-toolchain.cmake

@@ -1,3 +1,6 @@
+# cmake/clang-18-toolchain.cmake                              -*-cmake-*-
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
 include_guard(GLOBAL)
 
 set(CMAKE_C_COMPILER clang-18)

cmake/clang-19-toolchain.cmake

@@ -1,3 +1,6 @@
+# cmake/clang-19-toolchain.cmake                              -*-cmake-*-
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
 include_guard(GLOBAL)
 
 set(CMAKE_C_COMPILER clang-19)