v0.5.2 — Citation and package discovery

What changed

• Added CITATION.cff for machine-readable citation.
• Added package classifiers, keywords, repository URLs, and release badges.
• Kept the v0.5 decision-packet schema, thresholds, and CLI behavior unchanged.

Verification

python -m pytest -q
python -B -m r2d validate examples/fictional-ai-governance-research-to-decision/decision_brief.json
python -m pip wheel . --no-deps -w dist

Verified locally on 2026-07-16: 22 tests passed, CLI validation passed, and one wheel built successfully.