feat(tools): add component schema diff generator with shared core library

- Add @adobe/spectrum-component-diff-generator CLI tool for comparing component schemas
- Add @adobe/spectrum-diff-core shared library for common diff functionality
- Dynamic file discovery using GitHub API to detect new/deleted components
- Breaking vs non-breaking change detection for JSON schemas
- Support for remote-to-remote, remote-to-local, and local-to-local comparisons
- Professional markdown, JSON, and CLI output formats
- Integration with GitHub Actions for automated PR comments
- Comprehensive test coverage with 29 passing tests
- Monorepo integration with Moon and standardized tooling
- Remove ESLint in favor of Prettier for consistent formatting

Author: GarthDB

.changeset/component-diff-generator-initial.md

@@ -0,0 +1,35 @@
+---
+"@adobe/spectrum-component-diff-generator": minor
+"@adobe/spectrum-diff-core": minor
+---
+
+feat(tools): add component schema diff generator with shared core library
+
+**New Tools:**
+
+- `@adobe/spectrum-component-diff-generator` - CLI tool for comparing component schemas between versions/branches
+- `@adobe/spectrum-diff-core` - Shared library providing common diff functionality across tools
+
+**Key Features:**
+
+- Dynamic file discovery using GitHub API
+- Breaking vs non-breaking change detection for JSON schemas
+- Support for remote-to-remote, remote-to-local, and local-to-local comparisons
+- Professional markdown, JSON, and CLI output formats
+- Integration with GitHub Actions for automated PR comments
+- Comprehensive test coverage with AVA
+
+**CLI Usage:**
+
+```bash
+# Compare between versions
+sdiff report --osv v1.0.0 --nsv v1.1.0 --format markdown
+
+# Compare between branches
+sdiff report --osb main --nsb feature-branch --format json
+
+# Local comparisons
+sdiff report --osv v1.0.0 --local packages/component-schemas
+```
+
+This enables automated component schema change detection and reporting across Adobe Spectrum's design system workflow.