Add license string support in aw.yml manifest parsing and schema

[Copilot]

aw.yml package manifests did not accept a license field, so manifests including license metadata failed strict schema validation. This change adds first-class support for license as a string and propagates it through manifest parsing.

• Schema update

  • Added license to pkg/parser/schemas/aw_manifest_schema.json as type: string, preserving root-level strictness (additionalProperties: false) while allowing the new field.

• Manifest model + parser

  • Added License to internal manifest and resolved package structs in pkg/cli/add_package_manifest.go.
  • Parsed license from the manifest root when present and surfaced it in resolved package metadata.

• Coverage for expected behavior

  • Extended pkg/cli/add_package_manifest_test.go to verify:
    • valid string license is accepted and mapped (license: MIT)
    • non-string license values are rejected by schema validation

name: Repo Assist
license: MIT
includes:
  - workflows/review.md