feat: add gitignore-style negation patterns for workspace.files

[christso]

Summary

• Add glob pattern matching with gitignore-style negation to workspace.files configuration
• Patterns like **/*.md, !**/*.instructions.md, and re-inclusion work as expected
• Object entries {source, dest} continue to work as explicit single-file mappings

Example Usage

workspace:
  source: ./config
  files:
    - "**/*.md"
    - "!**/*.instructions.md"
    - "important.instructions.md"  # re-include specific file

Changes

File	Change
package.json	Add fast-glob dependency
src/utils/glob-patterns.ts	New file - pattern resolution utilities
src/core/transform.ts	Update copyWorkspaceFiles() to handle globs
tests/unit/utils/glob-patterns.test.ts	Unit tests (16 tests)
tests/unit/core/transform-glob.test.ts	Integration tests (15 tests)

Test Plan

• All 112 unit tests pass
• Glob pattern matching works correctly
• Negation exclusion works correctly
• Re-inclusion after negation works correctly
• Directory structure preserved when copying
• Dry-run mode reports correct destinations
• Backward compatible with literal paths and object entries