Policy Packs & Enforcement Modes (Advisory/Mixed/Hard)

[djm81]

Why

Policy enforcement needs reusable packs and per-rule modes without inventing a second clean-code-specific severity system.

What Changes

• Keep advisory, mixed, and hard enforcement modes as the only mode model.
• Add the built-in specfact/clean-code-principles pack with per-rule mode mapping.
• Let clean-code consumers inherit defaults from profile-01-config-layering and override modes through .specfact/policy.yaml.

OpenSpec Change Proposal: policy-02-packs-and-modes

[djm81]

Dependency mapping from CHANGE_ORDER: blocked by nold-ai/specfact-cli#237, nold-ai/specfact-cli#176.