docs: link Plotly/ECharts to their OSS docs; trim chart-datum comment

- analytics.md: make the Plotly and ECharts chart-library references
  links to plotly.com/javascript and echarts.apache.org; minor wording
  tidy (hardcode).
- charts/types.ts: trim the ChartClickDatum doc comment.

Co-authored-by: Isaac
Signed-off-by: Atila Fassina <atila@fassina.eu>

Author: atilafassina

docs/docs/plugins/analytics.md

@@ -558,7 +558,7 @@ createApp({
 });
 ```
 
-This is **pure response decoration**: the injected metadata never enters the cache key and never changes the SQL. With it wired, every metric `result` message carries a `metadata` field scoped to the requested columns; without it, the message is byte-identical to a plain `/query` result and the hook's `metadata` is `undefined`. Because the metadata rides on the payload, the client never has to import the generated file or hard-code a format string — it is **payload-carried and client-agnostic**.
+This is **pure response decoration**: the injected metadata never enters the cache key and never changes the SQL. With it wired, every metric `result` message carries a `metadata` field scoped to the requested columns; without it, the message is byte-identical to a plain `/query` result and the hook's `metadata` is `undefined`. Because the metadata rides on the payload, the client never has to import the generated file or hardcode a format string — it is **payload-carried and client-agnostic**.
 
 ### Format utilities
 
@@ -614,7 +614,7 @@ function RevenueTable() {
 
 Because `metadata[col].format` is just a string on the payload, the same spec drives axis ticks and tooltips in any chart library.
 
-**Plotly** — pass the spec straight through as a d3 `tickformat` / `hovertemplate` (Plotly axes speak d3-format):
+**[Plotly](https://plotly.com/javascript/)** — pass the spec straight through as a d3 `tickformat` / `hovertemplate` (Plotly axes speak d3-format):
 
 ```tsx
 import Plot from "react-plotly.js";
@@ -650,7 +650,7 @@ function RevenuePlot() {
 }
 ```
 
-**ECharts** — use the format spec inside `axisLabel.formatter` / `tooltip.formatter` via `formatValue`:
+**[ECharts](https://echarts.apache.org/)** — use the format spec inside `axisLabel.formatter` / `tooltip.formatter` via `formatValue`:
 
 ```tsx
 import ReactECharts from "echarts-for-react";

packages/appkit-ui/src/react/charts/types.ts

@@ -117,9 +117,7 @@ export interface ChartBaseProps {
 /**
  * A normalized description of a clicked chart element.
  *
- * This is the public, ECharts-free shape emitted by chart click handlers. It is
- * the single boundary that keeps ECharts event types out of appkit-ui's public
- * API — consumers should read the strongly-typed fields below and reach for
+ * Consumers should read the strongly-typed fields below and reach for
  * {@link ChartClickDatum.raw} only when they knowingly opt into unsupported
  * internals.
  *