Migrate mojo-yaml to Mojo 1.0 baseline

[Mjboothaus]

Summary

• migrate YAML parser/value/tests/examples to Mojo 1.0-compatible syntax and APIs
• apply boxed recursive value pattern for Mojo 1.0 deinit safety
• align pixi and recipe metadata with stable Mojo 1.0 policy

Validation

• pixi run test-all
• pixi run build-package

Co-Authored-By: Oz oz-agent@warp.dev

[semanticdiff-com]

Review changes with  

Changed Files

File	Status
.pre-commit-config.yaml	47% smaller
scripts/pre_submit_checklist.py	11% smaller
recipe.yaml	8% smaller
.github/workflows/test.yml	0% smaller
.github/workflows/validate-recipe.yml	0% smaller
CHANGELOG.md	Unsupported file format
RECIPE_SETUP.md	Unsupported file format
benchmarks/benchmark_parser.mojo	Unsupported file format
docs/JUST_SETUP.md	Unsupported file format
docs/PLATFORM_BUILDS.md	Unsupported file format
docs/RECIPE_VALIDATION.md	Unsupported file format
docs/pixi-pre-submit.md	Unsupported file format
examples/basic_usage.mojo	Unsupported file format
examples/nested_data.mojo	Unsupported file format
examples/quickstart.mojo	Unsupported file format
examples/read_file.mojo	Unsupported file format
justfile	Unsupported file format
packaging/recipe.yaml	0% smaller
packaging/test_package.mojo	Unsupported file format
pixi.lock	Unsupported file format
pixi.toml	Unsupported file format
scripts/build-recipe.sh	Unsupported file format
scripts/run_examples.py	0% smaller
scripts/validate-recipe.sh	Unsupported file format
src/yaml/__init__.mojo	Unsupported file format
src/yaml/lexer.mojo	Unsupported file format
src/yaml/parser.mojo	Unsupported file format
src/yaml/value.mojo	Unsupported file format
test_package.mojo	Unsupported file format
tests/test_debug.mojo	Unsupported file format
tests/test_failing_patterns.mojo	Unsupported file format
tests/test_fixtures.mojo	Unsupported file format
tests/test_inline_debug.mojo	Unsupported file format
tests/test_lexer_basic.mojo	Unsupported file format
tests/test_lexer_indentation.mojo	Unsupported file format
tests/test_lexer_scalars.mojo	Unsupported file format
tests/test_lexer_structural.mojo	Unsupported file format
tests/test_parser_basic.mojo	Unsupported file format
tests/test_parser_nested.mojo	Unsupported file format
tests/test_real_fixtures.mojo	Unsupported file format
tests/test_spaces.mojo	Unsupported file format
tests/test_version.mojo	Unsupported file format
tests/test_working_fixture.mojo	Unsupported file format
tests/test_yaml_value.mojo	Unsupported file format