class FSSearch

Existing features (ref: opencode grep tool):

1. Global result cap — limit total matches to 100 across all files.
2. Per-line truncation — truncate individual match lines longer than 2000 chars via rg --max-columns with preview.
3. Structured truncation message — when results are capped, append: "(Results truncated: showing 100 of N matches. Consider a more specific path or pattern.)"
4. Sort results by file mtime — most-recently-modified files first, so the LLM sees the most relevant matches first.
5. Return a plain string instead of a Hash.
6. Align output cap with universal truncation (2000 lines / 50 KB).