feat: add Scenario 2.0 composable packs

[DavidJBianco]

Summary

• add authored Scenario 2.0 composition while preserving Scenario 1.0 and direct runtime Scenario compatibility
• add fixed-schema industry/organization packs, exact deterministic resolution, immutable per-run effective configuration, and project/path/package repositories
• add pack management and resolve CLI workflows with stable JSON and provenance explanations
• ship finance, healthcare, technology, and Northstar Health sample packs
• emit and verify self-contained resolved scenarios and authoritative generation manifests; make evaluation bundle-first
• document composition and update installed skills for pack discovery/consumption, with dedicated pack-authoring skills retained as the next P1

Compatibility and safety

• no-pack Scenario 1.0 compilation does not instantiate or scan a pack repository and retains captured fixed-seed output hashes
• pack paths/includes are bounded and containment-checked; executable and unconstrained assets are rejected
• packs cannot modify engine-owned safety/evaluation policy or grant OOB authorization
• effective configuration and legacy/derived caches are isolated sequentially and concurrently
• authoritative bundles use registered transactional sidecars, portable provenance, and integrity hashes

Validation

• uv run ruff check .
• uv run ruff format --check .
• uv run pytest --no-cov — 5,563 passed, 21 skipped
• uv run pytest --no-cov tests/integration/test_smb_long_run.py --include-slow — 1 passed
• coverage gate — 85.22%, 5,563 passed, 21 skipped
• wheel/sdist build and sample-pack inventory verification
• fixed-seed finance and Northstar validation/generation smoke tests; bundle-only evaluation and resolved-input reproduction

Package versions intentionally remain at 1.17.0 on this feature branch. The 2.0.0 bump belongs in the final dev to main release commit after this and SMB work are integrated.