Bone Flow #027 textbox - partial repair candidate 1.0.60

Changes:
- #040 Caller gradient enabled on all five requested property triggers.
- Gradient RETURN is now retained in property controls and gradient state map.
- Runtime effect-color validator permits constrained linear-gradient syntax.
- Existing background support and unrelated component behavior retained.

NOT VERIFIED / OPEN:
- #022 HoverBorderEffect rendering of gradient colors (dependency not present in archive).
- #118 OPEN/CLOSE visual transitions in a browser.
- Windows PowerShell 5.1 Installer run and localhost integration.
- UI regressions, light/dark, scrolling and accessibility.
- Full functional behavior of all five properties.
DO NOT mark Completed/Frozen or ALL PASS.