capture_screenshot region:"chart" captures the first pane, not the active one

[stanzhang]

On a multi-pane layout, capture_screenshot with region: "chart" returns the first pane in the DOM, not the active one.

src/core/capture.js:

var el = document.querySelector('[data-name="pane-canvas"]')
  || document.querySelector('[class*="chart-container"]')
  || document.querySelector('canvas');

querySelector takes the first match, so on a 2x2 layout every region: "chart" capture is pane 0 regardless of pane_focus.

Reproduce

1. 4-pane layout, focus pane 3 (pane_focus), give it a different symbol or timeframe from pane 0.
2. capture_screenshot with region: "chart".

You get pane 0. It bit hardest with replay running on the active pane: the capture showed a live pane while the analysis was of a 2017 bar, and both looked entirely reasonable.

Suggested fix

TradingView marks the focused pane with an active class. This selector picks the right one on 3.3.0:

document.querySelector('.chart-container.active') || document.querySelector('.chart-container')

Reading getBoundingClientRect() off that element and passing it as the CDP clip gives a correctly cropped active pane; verified locally against a single-pane and a 4-pane layout.