feat: monorepo support — multiple spec files

[hermanngeorge15]

Description

Support monorepo setups where multiple spec files exist (e.g., one per package or service).

Acceptance Criteria

• Accept glob pattern for spec-file input (e.g., packages/*/CLAUDE.md)
• Run pipeline on each matched spec file independently
• Aggregate results into a single PR comment with per-spec sections
• Scope check uses relative paths per spec file location

Milestone

v0.1.0