Memory types, and tags retire

Every Memory now has a type — Decision, Asset, Fact, or Context — that says what kind of content it holds, shown as a chip on every card and the detail view, and filterable in both your Personal Space and Shared Spaces. Type is auto-classified the moment a memory is captured (by you or an agent via MCP — store_memory takes an optional type), and you can override it. The personal feed now also shows each memory's Topic. With type doing the "what kind of thing is this" job and Topics doing the grouping, free-text tags are retired from capture and the UI.