- search.md no longer claims "full regex syntax". Engine is rust-regex
(RE2) so lookaround and backreferences are unsupported; the doc now
says so and points at the post-filter alternative.
- search.ts rejects array entries containing a top-level comma with an
actionable ToolError, instead of silently demoting to a footer note
and returning zero matches.
- Add a paths-as-array example to search.md.
