Add property filter support to query_nodes MCP handler #1036

Summary

The query_nodes MCP tool currently only supports content contains and title contains filters. Property-level filters (e.g., status equals in_progress) are silently ignored, causing agents to get incorrect results.

The backend already has a robust PropertyFilter system (FilterOperator::Equals, NotEquals, Contains, etc.) in models/node.rs, but it's not wired up in the MCP handler.

Problem

When an AI agent queries for tasks with status: in_progress, it sends:

{ "filters": [{ "field": "status", "operator": "equals", "value": "in_progress" }] }

This filter is silently ignored and all tasks are returned, leading to incorrect results.

Acceptance Criteria

• query_nodes MCP handler supports property filters via the existing PropertyFilter system
• Supported operators: equals, not_equals, contains, starts_with, ends_with
• Unsupported filter fields/operators return a clear error instead of being silently ignored
• Tool description/schema updated to document supported property filters
• Tests cover property filtering through MCP

Context

• PropertyFilter implementation: packages/core/src/models/node.rs:603
• Query service with property filters: packages/core/src/services/query_service/mod.rs
• MCP handler: packages/core/src/mcp/handlers/nodes.rs:523