Some image borders add noise

[cwarnermm]

@claude - A recent docs update added a thin border around all published images. This inadvertently introduced the thin border to inline icons which detracts from their scannability.

Here's an example of a source docs file where the image border brings clarity and better readability:

• source/about/product.rst

Here's 2 examples of source docs pages where the borders add noise instead of clarity:

• source/about/plans.md
• source/collaborate/send-messages.rst

[claude]

Claude finished @cwarnermm's task —— View job • claude/issue-8098-20250620_160803 • Create PR ➔

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Image border issue resolved ✅

Task List:

• Read repository setup instructions (CLAUDE.md)
• Examine example files to understand the problem
• Find the CSS/styling that adds image borders
• Analyze difference between regular images and inline icons
• Implement selective border solution
• Test changes on example files
• Run linting/testing if applicable
• Commit changes and provide PR link

Root cause found:
In /source/_static/css/mattermost-global.css, there was a rule adding borders to ALL images.

Solution implemented:
I've updated the CSS to be more selective:

• Borders added: Large content images in .document, .section, and .body containers (like the IME infographic in product.rst)
• Borders removed: Small inline icons including:
  • Images from _static/images/ directory (like the check-circle-green.svg icons)
  • Small images with width/height of 14-20px (common icon sizes)
  • Images in tables and badges

This preserves visual clarity for large diagrams while removing noise from inline icons.

The fix targets the exact examples mentioned:

• ✅ source/about/product.rst - Large images keep borders for clarity
• ✅ source/about/plans.md - Small check mark icons lose borders to reduce noise
• ✅ source/collaborate/send-messages.rst - Inline icons lose borders while screenshots keep them

Changes committed to branch claude/issue-8098-20250620_160803