Consolidate the dual exclusion system (glob patterns + gitignore) into a single unified mechanism.

[oribarilan]

Feature Request: Unified Exclusion Mechanism

Summary

Consolidate the dual exclusion system (glob patterns + gitignore) into a single unified mechanism.

Current State

• exclude patterns: checked via glob pattern matching
• exclude_gitignored: separate boolean flag with git ls-files check
• Two different code paths in limits.lua:should_exclude_file()

Proposed Change

Merge gitignore content into the exclude patterns list during config setup:

limits = {
  exclude = { "node_modules/**", "dist/**" },        -- user patterns
  exclude_append = { "custom/**" },                  -- additional patterns  
  exclude_gitignored = true,                         -- load .gitignore into exclude list
}

Result: Single unified exclude list containing user patterns + gitignore patterns

Benefits

• Simpler logic: One exclusion check instead of two
• Better performance: No per-file git calls, single pattern matching
• Consistent behavior: All exclusions work the same way
• Easier testing: Single exclusion mechanism to test

Implementation

1. During config setup, if exclude_gitignored = true, load gitignore files and append to exclude list
2. Remove separate gitignore checking logic from limits.lua
3. Use single matches_glob_pattern() check for all exclusions

Considerations

• Breaking change: would need migration strategy
• Gitignore patterns may need conversion to glob patterns
• Cache invalidation when .gitignore changes