Type page chat: "Ask about <type> type...", hide it when AI Chat is off in Labs, rename nav to "Types and Views" #3839

Changes

• The chat button on a type's own page (query-node-viewer.svelte, bound to the schema) reads "Ask about type..." instead of "Ask".
• The side nav parent item "Node Types" is renamed "Types and Views".

Acceptance Criteria

• Type page button label shows the type's display name, e.g. "Ask about Task type..."
• A saved query's button label is unchanged unless decided otherwise
• Side nav parent item reads "Types and Views"
• Tests asserting the old strings are updated