0.4.4 — adapter examples degrade cleanly; Beta + Security on PyPI

Polish pass on the first-run experience and PyPI discoverability. No engine change.

• Adapter examples stop crashing without the framework. veto_crewai.py and veto_langgraph.py moved their framework import into main() behind a try/except — a pip install gate-cat user running the example now gets a one-line "install gate-cat[crewai]/[langgraph] to run this adapter demo; the gate itself needs none of it" instead of a raw ModuleNotFoundError. Verified: both print the clean message with no framework installed.
• Hook example README dropped the >= 0.3.0 note and the "fix the absolute path to veto_hook.py" step that contradicted settings.example.json (it calls the gatecat-hook console script by name — nothing to edit).
• PyPI metadata: Development Status Alpha → Beta, added Topic :: Security and Quality Assurance classifiers + security keywords (verified live on the 0.4.4 JSON API). So the package shows up as the guardrail it is.

Clean-venv verified: pip install gate-cat==0.4.4 → hero snippet raises VETO [TERRAFORM_PROD]. Tests 907/27/0 local.