Clean up non-code files (#5801)

* Clean up README, contribution guide, and repository metadata

- REUSE.toml: fix the Hedley path and SPDX id (CC0-1.0), mark the docset
  icons as the public-domain JSON logo
- CITATION.cff: v3.12.0 was released on 2025-04-11
- FILES.md: list all workflows, describe the Meson option defaults
- README: ctest -LE, table of contents, typos, stale Android/MinGW advice,
  moved links, merge duplicate Thanks entries, list the analysis tools
  used in CI
- CONTRIBUTING: iterative parser, json_literals.hpp is generated, links
- .gitignore: backups and release outputs; .gitattributes: mark
  generated files
- labeler: label other build systems and .github documentation
- MODULE.bazel: add the module version

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Clean up CI, CMake, Makefile, and Bazel files

- CMakeLists.txt: avoid VERSION_GREATER_EQUAL, which CMake < 3.7 lacks
- ci.cmake: test JSON_DisableTupleReferenceConversion in ci_cmake_flags,
  remove unused variables and unreachable per-compiler targets, look up
  Clang tools consistently, forward CMAKE_CXX_FLAGS to ci_module_cpp20,
  format json_literals.hpp and remove backups in ci_test_amalgamation
- BUILD.bazel: add json_literals.hpp to the single-header target
- workflows: format json_literals.hpp before copying it, drop the obsolete
  natvis --version plumbing, name natvis and macro_builder in failure
  messages, drop the duplicate amalgamation job, install Valgrind only
  where needed, republish docs on version bumps, fix stale names
- Makefile: complete .PHONY and help, check-amalgamation always restores
  the checked-in files, natvis uses its own venv, macro_builder_check
  installs astyle, clean removes the fuzzer binaries
- remove tools/amalgamate/config_json_view.json (json_view.hpp is not on
  develop yet)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix inaccuracies in the documentation

- version history: json_base_class_t (3.11.3), JSON_HAS_CPP_11 (3.10.0),
  JSON_HAS_RANGES exclusions, define-type macros, ABI tags
- releases: 3.12.0 raised the minimum CMake version
- from_*: the (ptr, len) overloads are deleted, not removed, in 4.0.0
- contains/count/find: document the deleted integral overloads
- add JSON_HAS_RANGE_VIEW_CONVERSION and list the JSON_HAS_* macros in
  the macro overview
- mention BON8 and error_handler where binary formats are listed
- broken links, outdated URLs, warning count, Hunter v0.26.12
- copy_markdown_source hook: expand snippets in the Markdown copies

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Pass /EHsc to the Windows C++20 module build

ci_module_cpp20 now forwards CMAKE_CXX_FLAGS to the module build. The
Windows workflow sets CMAKE_CXX_FLAGS, which replaces CMake's MSVC
defaults including /EHsc, so <chrono> failed with C4530 under /WX.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

FILES.md

@@ -14,7 +14,7 @@ This file describes the source for supporting files; that is, files that are not
 The [GitHub Actions](https://docs.github.com/en/actions) workflows that build, test, and analyze the library. Each file in this folder defines one workflow:
 
 - `ubuntu.yml`, `macos.yml`, `windows.yml` — build and run the test suite on Linux, macOS, and Windows.
-- `check_amalgamation.yml` — verify that the single-header amalgamation in `single_include` is up to date on pull requests.
+- `check_amalgamation.yml` — verify on pull requests and pushes to `develop` that the generated files (the single-header amalgamation in `single_include`, `BUILD.bazel`, and `nlohmann_json.natvis`) are up to date.
 - `comment_check_amalgamation.yml` — comment on a pull request when the amalgamation check failed.
 - `cifuzz.yml` — run short fuzzing sessions via [OSS-Fuzz CIFuzz](https://google.github.io/oss-fuzz/getting-started/continuous-integration/) on pull requests.
 - `codeql-analysis.yml` — run [CodeQL](https://codeql.github.com) code scanning.
@@ -24,7 +24,9 @@ The [GitHub Actions](https://docs.github.com/en/actions) workflows that build, t
 - `dependency-review.yml` — scan dependency changes in pull requests for known vulnerabilities.
 - `labeler.yml` — the "Pull Request Labeler" workflow (see `.github/labeler.yml`).
 - `stale.yml` — comment on and close stale issues and pull requests.
-- `publish_documentation.yml` — build and publish the documentation on every merge to the `develop` branch.
+- `publish_documentation.yml` — build and publish the documentation on pushes to the `develop` branch that touch the documentation sources (or the files it embeds).
+- `check_docs_links.yml` — check the links of the documentation weekly, as external links can break without any change in this repository.
+- `cancel_closed_pr_runs.yml` — cancel unfinished workflow runs of a pull request once it is closed or merged.
 
 Further documentation:
 
@@ -266,8 +268,9 @@ meson setup builddir
 ninja -C builddir
 ```
 
-`meson_options.txt` defines the options, which mirror the CMake options that change the library's target (for example,
-`-DDiagnostics=true`). Meson requires this file next to `meson.build`, so it is also part of `include.zip`. `make check_build_options`
+`meson_options.txt` defines the options, which mirror the names of the CMake options that change the library's target (for example,
+`-DDiagnostics=true`); their defaults may differ (for example, `MultipleHeaders` defaults to `false` in Meson, while
+`JSON_MultipleHeaders` is `ON` in CMake). Meson requires this file next to `meson.build`, so it is also part of `include.zip`. `make check_build_options`
 ([`tools/check_build_options`](tools/check_build_options/README.md)) checks in CI that both files and the pkg-config files
 stay in sync with the CMake options.