Graphics: Replace 98.css default elements with PV8 visual assets

[jessefreeman]

Scope:
Replace default 98.css graphics, borders, and visual elements with Pixel Vision 8's unique art style and color palette.

Key Actions:

• Audit all 98.css visual assets (borders, buttons, window chrome, icons)
• Create PV8-styled replacements maintaining same dimensions and behavior
• Update CSS variables and background images with PV8 assets
• Ensure pixel-perfect rendering at target resolutions
• Maintain accessibility contrast ratios

Visual Elements to Replace:

• Window borders and title bars
• Button backgrounds and borders
• Input field styling
• Scrollbar elements
• Modal/dialog borders
• Icon set (where applicable)

Acceptance Criteria:

• All default 98.css graphics replaced with PV8 equivalents
• Visual consistency across all replaced elements
• No broken layouts or sizing issues
• Maintains original component functionality
• Test page updated to show PV8-styled components

Deliverables:

• PV8 graphic assets (PNG/SVG as appropriate)
• Updated CSS with PV8 visual styling
• Asset organization and naming conventions
• Updated test page demonstrating PV8 styling

Dependencies:

• Requires Setup: Integrate 98.css framework and create UI testing environment #8 (setup) to be completed first

Parent epic: #7