docs: record 0.1.2 release evidence

[tensornull]

Summary

• mark 0.1.2 stable maintenance complete
• record the Release Please transport hardening and exact reviewed release identity
• record immutable GitHub Release, exact-release live smoke, PyPI OIDC publication, public digests, provenance, and independent install evidence
• confirm release/live variables are disabled and recovery state was not used

Why

The immutable 0.1.2 release and public PyPI artifacts are now fully verified.
These post-release docs preserve the remote, live, and registry evidence without
changing the released artifact or starting 0.2 work.

Validation

• uv sync --locked
• Ruff check and format check
• strict Pyright
• 332 non-live tests
• version, public-doc, releasable-doc, secret, and workflow semantic checks
• actionlint 1.7.12
• wheel/sdist build, Twine, artifact inspection, independent clean installs, and README examples
• copied standalone repository verification
• git diff --check
• independent claim-by-claim GitHub/PyPI evidence review