The new descriptions called Catch3 "Catch2's test API with a parallel
runner", which reads as if it were Catch2. Catch3 is a C++ test framework
whose test-writing API is compatible with Catch2's. CMake, Doxygen and both
pkg-config files now say so; the with-main file no longer carries Catch2's
own tagline.

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

Remove what Catch2's maintainers left that is not ours

Catch3 is maintained by Progmasoft, but the repository still carried
Catch2's funding links, its maintainer list and GPG keys, a Code of Conduct
contact at a Catch2 maintainer's address, its lists of users, its release
process and release scripts, its AppVeyor configuration and its logos.

- Removed FUNDING.yml, MAINTAINERS.md, appveyor.yml with the AppVeyor and
  OpenCppCoverage helpers, Catch2's user lists, why-catch, release process
  and deprecations pages, its two logos and the major/minor/patch release
  scripts. releaseCommon.py keeps only what the amalgamation reads.
- The Code of Conduct sends reports to support@progmasoft.com.
- contributing.md and release-notes.md are written for Catch3; Catch2's
  release history is linked upstream.
- CMake, pkg-config and Doxygen name Catch3 and its repository; the
  amalgamated files say which Catch3 version and which Catch2 engine they
  come from.

Replace Catch2's runner with the Catch3 runner

History::Commit went on writing when the lock was still held by another
run after ten seconds, so two runs that finished together could replace
each other's record. It now returns an error instead, which the runner
reports as a history that was not saved. The wait is a parameter, so the
new unit test can hold the lock and see the commit refused.

Listeners that print while they are created raced with the first test:
the text went through the worker's error stream and could reach the
runner after it had given the worker a test, which then claimed it as its
own output. The worker now captures Catch2's standard streams while it
creates the listeners and starts the run, sends the text in its hello
message, and the runner writes it to its standard error.

Catch2's stream redirect now remembers the buffer to restore when a
redirect starts rather than when it is made, so a stream whose buffer
changed in between is restored to the right one.

A test that called exit() crashed its worker with SIGSEGV on Linux and
macOS. The exit hook read Catch2's captured output through a scoped
deactivation, which switched the capture back on; libstdc++ then flushed
std::cout at exit into a capture buffer that static destruction had
already freed. RunContext::endCapture() now ends the capture for good and
returns what it held, so the standard streams are their own again.

A JUnit, JSON or trace report that could not be written was only
reported on stderr, and a run whose tests passed still exited with 0, so a
build server could miss it. Such a run now exits with 1; failed tests
still exit with 42.

Integration tests of the runner's output move their helpers into
RunnerFixtureClient.hpp and cover --version, --help, the listing modes, a
bad option, exit codes 1 to 4, -v, -q, --slowest, colours, --analytics
in text and JSON, and Bazel's test environment.

ExtraTests X21 and X27 defined their listeners at namespace scope, which
clang rejects under -Wweak-vtables with -Werror on Linux and macOS; they
are now in anonymous namespaces.

After a fatal signal Catch2 closes the open sections itself, so on POSIX a
crash was reported outside the section it happened in. The scheduler now
ignores section ends that follow a fatal condition.

New unit tests cover the planner (every selection, dependency closure and
cycles, hash and duration shards, incremental runs, learned time limits,
ordering, retries, quarantine and replay), every command-line option and
its errors, and the failure analysis (history classes, signature groups,
crash and hang locations, changed files, replay commands).
Catalog::FromEntries builds a catalog without a test registry so the
planner can be tested on its own.

The license check expects Progmasoft's header only on paths that contain
a Progmasoft directory, so the two runner fuzzers move next to each other
under fuzzing/Progmasoft and keep their MPL header.

Catch3 keeps Catch2's API for writing tests (test cases, sections,
assertions, matchers, generators, listeners, benchmarks) and replaces its
session, command line and reporters with a runner of its own.

The runner starts the test binary again as worker processes that take the
next test when they are free. A crash, an exit or a hang ends one test, not
the run. On top of that it adds:

- retries that tell deterministic, flaky and order-dependent failures
  apart, and a bisection that names the test leaving state behind;
- a history of verdicts and durations, kept under a file lock, that drives
  automatic quarantine, adaptive time limits, predictive ordering,
  incremental runs, failure replay and analytics;
- selection by change, past failure or prediction, dependency closure,
  and sharding by a stable hash or by recorded durations;
- tags for serial and isolated tests, shared resources, dependencies,
  time limits and retries;
- a failure category, a signature, an analysis and a replay command for
  every failure;
- console, JUnit XML (with flakyFailure and rerunFailure), JSON and Chrome
  trace reports, and a versioned discovery listing (--list=json);
- a temporary directory per test (TMPDIR, TMP, TEMP and
  TestTemporaryDirectory());
- Bazel's test environment: XML output file, test filter, sharding, seed,
  premature exit file and undeclared outputs.

The command line is parsed by a hand-written, typed parser. Catch::Session
remains as a thin facade over the runner for custom main functions.

The result model in Progmasoft/Catch3/Results.hpp was rewritten around
tests and attempts, and the JUnit writer now writes it. The property
engine's example database is updated under a file lock with an atomic
rename, so parallel workers can write it at the same time.

Removed: Clara, the command-line and reporter-spec parsers, every reporter
and CATCH_REGISTER_REPORTER, listing, text flow, console colour and width,
the JSON and XML writers, sharding in the test registry, approval tests and
their baselines, Conan packaging, and the unused third_party/clara.hpp.
Listeners keep working; reporters' list and skip events are gone.

The Catch2 library is now compiled as C++20; code that includes only
Catch2's headers still needs C++14. Duplicate test cases are still refused
at start-up. Version 0.3.0.

ExtraTests now turn exceptions off for clang-cl with MSVC-style options,
which -fno-exceptions did not do.