Why

The memories MCP search tool only accepts a single substring today, which makes it hard for clients to express combined queries or explain why a line matched. This change adds the richer search shape needed for the next client iteration while keeping the legacy single-query call working.

What changed

• accept either the legacy query field or a new queries array, plus match_mode: any|all
• teach the local memories backend to evaluate multi-query line matches and return matched_queries on each hit
• update the MCP input/output schema and add coverage for parser behavior, ordering, pagination, case sensitivity, and match modes

Testing

• added unit coverage in memories/mcp/src/local_tests.rs and memories/mcp/src/server.rs