Adds Chart plugin

[BhattaraiSijan]

Purpose

Adds the Chart plugin — receiver-only consumer of plugin:aoi:analysisReady. Renders the AOI plugin's per-layer statistics payload as cards with a histogram and stat grid. No fetching, no per-layer config; purely a display surface for what AOI publishes.

Proposed Changes

• [ADD] src/essence/Tools/Chart/ — new plugin
  • ChartTool.js — MMGIS wrapper. Module-level subscription to plugin:aoi:analysisReady (so the event reaches Chart even when AOI is the active tool), stashes the latest payload, auto-opens the Chart panel via toolButtonChart, mounts React.
  • ChartComponent.tsx — presentational panel. Header + one card per (layer, asset):
    • headline mean + "X% valid · N pixels"
    • histogram bar chart via chart.js (tooltip shows the bin's lo–hi range and pixel count)
    • 6-stat grid: min / max / median / std / 2nd %ile / 98th %ile
  • chartHelpers.ts — pure helpers
  • ChartComponent.css

Bus surface

• Listens (module scope): plugin:aoi:analysisReady { analysisData: { [layerName]: <stats | null> } }
• No emits, no provides, no requests.

Issues

• Develop time series chart plugin #82

Testing

Manually tested on a DeckGL mission with two analysis-supported layers:

• AOI → draw → Analyze area → Chart panel auto-opens with cards (Chart was not the active tool at click time)
• Multi-band layer (colorir, bidx 1/2/3) → three cards, one per band; single-band layer (dnbr) → one card
• Layer whose /statistics POST returns non-2xx (or its entry is null in the payload) → the layer's card shows "Could not fetch statistics for this"; other layers still render
• 200 with valid_pixels === 0 → card shows "No usable pixels in this area"
• Tested on macOS, Chrome

Known follow-ups (not blocking)

• Card titles show the layer UUID instead of the display name — owned on the AOI side (analysisData payload is keyed by layer.name, which MMGIS internally rewrites to the UUID). Fix is display_name || name on the emit, to land on a future AOI iteration.
• Module-level subscription uses a setInterval retry while window.mmgisAPI finishes binding — should become mmgisAPI.whenReady() once the bus exposes a ready contract.