fix(oxygen): hide disabled shade and tint variables

[Jan-CoreBunch]

Problem

After a Figma save, Oxygen Classic's synchronized global colors correctly contain only active colors, but Core Framework's variable autocomplete can still list obsolete shade and tint variables. Presets retain their shades and tints arrays when isShades or isTints is disabled, and the PHP helpers previously enumerated those arrays without checking the flags. The generated CSS already respects the flags, leaving dropdown entries that point to nonexistent custom properties.

The Alt-click Core Framework Variable UI had the same visible symptom because it rendered the retained color-system arrays directly.

Solution

• Gate shades on isShades === true and tints on isTints === true in both variable-list helpers.
• Apply the same rule to the equivalent flat and grouped class-name helpers so their output matches generated CSS.
• Gate shade and tint rendering in Oxygen Classic's Alt-click Variable UI.
• Rebuild the tracked Oxygen Classic integration bundle.
• Add PHP regression coverage for enabled, disabled, and missing variation flags across flat/grouped variables and classes.

This does not mutate or clean up persisted preset data; it only prevents disabled variants from being exposed as usable variables or classes.

Validation

• PHP unit suite: 40 tests, 82 assertions
• Targeted PHP coding standards: passed
• Focused TypeScript check for Bricks/Oxygen shared globals and Oxygen Classic: passed
• Builder integration production build: passed
• Git diff whitespace check: passed