Adds engine.allowed-models — an allowlist of model glob patterns the workflow may use. Any model not matching at least one pattern is rejected by the AWF firewall with HTTP 403 (model_blocked_by_policy). Backed by gh-aw-firewall#4406.

Example

engine:
  id: copilot
  allowed-models:
    - copilot/gpt-*
    - copilot/claude-sonnet-*

Pattern syntax: provider/glob, */glob, or bare glob. * is case-insensitive within a segment.

Changes

• engine.go — AllowedModels []string added to EngineConfig; parsed from allowed-models key in object-format engine frontmatter
• awf_config.go — AllowedModels added to AWFAPIProxyConfig (json:"allowedModels,omitempty"); populated in BuildAWFConfigJSON
• awf-config.schema.json — allowedModels added to apiProxy properties to pass schema validation

Note: This PR is draft pending merge of the upstream AWF firewall PR that adds enforcement.