fix: implement true grid pattern for Grid and Cross brushes

[fank]

Summary

Fixes Grid and Cross brush patterns to display correctly on ELLIPSE and RECTANGLE markers, matching Arma 3's in-game appearance with a crosshatch pattern overlay.

Problem

1. Pattern not visible: The map uses preferCanvas: true for performance, but Canvas rendering doesn't support SVG patterns. The patterns were being created but never displayed.

2. Wrong pattern type: The previous implementation used L.StripePattern which only draws lines in one direction. Grid/Cross brushes need both horizontal and vertical lines.

Solution

1. SVG Renderer for Patterned Shapes

Created a dedicated SVG renderer (window.svgRenderer) that's used only for shapes with pattern fills:

// In ocap.js - create SVG renderer for pattern support
window.svgRenderer = L.svg();
window.svgRenderer.addTo(map);

// In ocap.marker.js - use SVG renderer for patterned shapes
if (this._brushPattern && window.svgRenderer) {
    polygonOptions.renderer = window.svgRenderer;
    // Add pattern to SVG renderer's defs...
}

2. Custom GridPattern Class

Created L.GridPattern that draws both horizontal and vertical lines with a colored background:

L.GridPattern = L.Pattern.extend({
    options: {
        color: '#ffffff',        // Grid line color
        backgroundColor: null,   // Background fill color
        backgroundOpacity: 0.5,
        // ...
    },
    _addShapes: function () {
        // Background rectangle (if backgroundColor set)
        if (this.options.backgroundColor) {
            this._bg = new L.PatternRect({...});
            this.addShape(this._bg);
        }
        // Horizontal + Vertical lines
        this._hLine = new L.PatternPath({...});
        this._vLine = new L.PatternPath({...});
        this.addShape(this._hLine);
        this.addShape(this._vLine);
    }
});

3. L.SVG._updateStyle Patch

Patched the SVG renderer to apply pattern fills after style updates:

L.SVG.prototype._updateStyle = function(layer) {
    originalUpdateStyle.call(this, layer);
    if (layer.options && layer.options.fillPattern && layer._path) {
        const patternUrl = L.Pattern._getPatternUrl(L.stamp(layer.options.fillPattern));
        layer._path.setAttribute('fill', patternUrl);
    }
};

Visual Result

• Background: Marker color at 30% opacity (light)
• Grid lines: Marker color at 50% opacity (darker, visible pattern)

Also Included

• Add ELLIPSE to updateRender method (was only RECTANGLE)
• Add defensive checks for this._size array access
• Handle case-insensitive brush names (grid, Grid, GRID)

Test Plan

• Load recording with ELLIPSE markers using "grid" brush
• Verify markers display with crosshatch pattern (both H and V lines)
• Verify color is applied correctly (light background, darker grid lines)
• Verify pattern matches in-game appearance