fix llm guard ci checks

[poojakira]

what changed

• fixes CI paths after package layout moved from old src imports to llm_guard_scanner package imports
• updates red-team corpus gate to use the package CLI module instead of missing scan.py
• corrects coverage target to the installed package and adds deterministic CLI tests
• removes overstated demo wording and keeps mappings scoped to implemented checks

why

• current main CI was failing on missing files, stale imports, and a broken coverage target
• the repo is a flagship ML-security portfolio project, so green reproducible checks matter more than broad claims

risks/edge cases

• optional embedding and broader OWASP detector modules still have low direct test coverage; this PR does not claim full coverage
• local Python environment showed unrelated broken package warnings for existing site-packages, but repo tests pass offline

validation performed

• py -3.12 -m ruff check src tests demo.py verify.py
• py -3.12 -m ruff format --check src tests demo.py verify.py
• py -3.12 -m pytest -q: 84 passed, coverage 68.62% over 60% gate
• py -3.12 demo.py
• py -3.12 verify.py