docs: prepare README and CHANGELOG for 0.1.0 release

[LautaroParada]

Motivation

• Prepare the repository narrative and release notes so the project is ready for a public 0.1.0 release without performing any build or upload steps.
• Align documentation strictly with the existing package API and implementation, avoiding any claims or features not present in the codebase.
• Keep the change small and documentary only, touching no source code, tests, CI, packaging metadata, or examples.

Description

• Rewrote README.md to a sober, public-facing document that describes the package as variance-test, lists installation commands (pip install variance-test and pip install -e .), current scope, weak-form battery contents, usage examples consistent with the public API, examples list, interpretation notes, release status, local release process, and development notes.
• Created CHANGELOG.md and added an entry for ## [0.1.0] - YYYY-MM-DD with Added, Changed, and Notes subsections summarizing the actual implemented functionality (packaging under src/, public API, input_kind support, normalization utilities, weak-form battery v1, partial rolling support, examples, CI, and hardening).
• Ensured the documentation contains no emojis, icons, badges, decorative Unicode, or claims of automatic publication, and preserved the package 0.1.0 target as documentation only.
• Modified files: README.md, CHANGELOG.md, and no other files were changed.

Testing

• Ran the test suite with pytest -q, which completed successfully with 81 passed and 4 warnings.
• Confirmed no source, test, or CI files were modified and no build or upload steps were executed during this sprint.

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Codex Task