feat(grep): add --include/--exclude glob patterns

[chaliy]

Summary

• Add --include=GLOB and --exclude=GLOB options for grep -r recursive search
• Fix recursive grep to always show filenames (matching real grep behavior)
• Fix multi-file filename display to use actual input count instead of CLI arg count
• Add strip_quotes helper for = option values
• Add glob_matches and should_include_file helper functions

Test plan

• cargo fmt --check
• cargo clippy --all-targets --all-features -- -D warnings
• cargo test --all-features — all tests pass
• 17 grep unit tests pass (including 2 new recursive include/exclude)
• grep spec tests pass — 2 previously-skipped tests now active, 1 new test added