mutator 0.2.1

This release addresses feedback received from CRAN during the review of the initial submission:

Removed the default output directory from mutate_file(), so callers must explicitly choose where mutant files are written.
Restored the caller’s working directory immediately with on.exit() in all package test-runner and coverage code paths that temporarily change it.

mutator 0.2.0

Added first-class tinytest support. A package with an inst/tinytest directory is now auto-detected and its mutants are run in-process with pkgload::load_all() and tinytest::run_test_dir(), without an install per mutant, including coverage-guided test selection.
Added a strategy argument to mutate_package() to override test-framework auto-detection. Accepted values are "auto" (the default), "testthat", "tinytest", "tinytest-installed", and "installed".
Added a tinytest-installed strategy that installs each mutant and runs tinytest::test_package(). It is a fallback for packages whose in-process load diverges from an installed copy and unlike the generic installed-tests fallback it still supports coverage-guided selection.
Reworked the README and configuration vignette, documenting how the test strategy is selected and when to override it.
Fixed the per_file coverage backend to forward the package’s tests/testthat.R harness arguments (notably any filter) to testthat::test_dir(), matching the record_tests backend.

Fixed coverage-guided baseline runs for packages with native code by compiling native sources before mutant execution.
Fixed the record_tests coverage backend so it forwards the selected CRAN mode consistently.
Updated the reusable GitHub Actions workflow to install imputesrcref from its default branch, replacing the removed development-branch reference.
Expanded mutation-system coverage across execution modes and raised mutator’s own test coverage above 90% without adding slow integration tests.