feat: YAML template gallery — community ontology templates

[rajnavakoti]

Description

A collection of community-contributed YAML ontology templates for various domains. Shipped with the package and browsable. Users can submit templates via PR.

Acceptance Criteria

• cb templates list shows available templates
• cb init --profile <template-name> uses a community template
• Templates stored in templates/ directory in the package
• Template format documented with a contributing guide
• At least 5 templates: engineering, legal, healthcare, fintech, operations

Out of Scope

• Online template marketplace
• Template versioning