flint-chart: interactions and updates on a chart

A Flint chart is shared state. A reader's gesture becomes an event, a handler turns the event into an update { id, ops }, updates compose as layers, and the layers render into a state the host and the agent read back. An application and an agent write the same kind of update directly. The full model is in the documentation: https://microsoft.github.io/flint-chart/#/documentation/interaction-introduction

The chart itself (chart_spec, semantic_types) is the flint-chart-author skill. Everything here runs on the Vega-Lite backend; a static render and the other backends leave interaction_spec and updates untouched.

What you produce (and what you do NOT)

The request says	You produce	Section
A gesture or a behaviour on the chart: "highlight on click", "zoom", "brush a period", "make it interactive", "add behaviour to this chart".	One interaction_spec: { "interactions": [ ... ] }, presets only.	Add interactions to the chart
A change to a chart that is already on screen, from outside: "point out Japan", "frame 2010 to 2020", "note this value", "reorder by value", an agent answering a user with the chart.	One ChartUpdate: { "id", "ops": [ ... ] }.	Update the chart
Code around a chart: "in my app", "on click open the record", "a panel that follows the hover".	TypeScript against flint-chart/interactive: mount, presets as factories, onChange, dispatch.	Use Flint in an application
Code across charts or over time: "link these two charts", "a table that follows the selection", "play the years".	linkCharts or useLinkedCharts; dispatch on a timer. On an MCP board, link_spec instead (board skill, "Step 5, connect them").	Link charts
A gesture no preset gives: "drag along the path", "draw a guess", "a rule for the box", "a lens the app draws".	A CanvasInteractionDef: a trigger, affordances, a handler.	When no preset fits