Close patch 0.1.2 Rust install wording

[docushell-dev]

Summary

• update README and public boundary claims so Rust crate install examples use published 0.1.2 crates
• add a source-bound Rust public install wording closeout validation record and release-candidate guard
• keep Python/PyPI at ethos-pdf==0.1.1 and preserve hosted, production, Windows, bundled PDFium, benchmark, ethos-doc, and ethos-rag blockers
• adjust older 0.1.2/0.1.1 wording guards to validate their historical records instead of freezing current README state

Tests

• PYTHONDONTWRITEBYTECODE=1 python3 .github/scripts/test_patch_0_1_1_public_install_wording_closeout.py
• PYTHONDONTWRITEBYTECODE=1 python3 .github/scripts/test_patch_0_1_2_readiness_prep.py
• PYTHONDONTWRITEBYTECODE=1 python3 .github/scripts/test_patch_0_1_2_version_activation.py
• PYTHONDONTWRITEBYTECODE=1 python3 .github/scripts/test_patch_0_1_2_rust_public_install_wording_closeout.py
• PYTHONDONTWRITEBYTECODE=1 python3 .github/scripts/test_patch_0_1_2_public_install_wording_closeout.py
• PYTHONDONTWRITEBYTECODE=1 python3 .github/scripts/test_public_surface_posture.py
• PYTHONDONTWRITEBYTECODE=1 python3 .github/scripts/public_boundary_claims_gate.py
• PYTHONDONTWRITEBYTECODE=1 python3 .github/scripts/claims_gate.py
• git diff --check
• make light-check PYTHON=python3
• make release-candidate-prep PYTHON=python3