Environment propagation for font, color, and disabled

[colemancda]

Style modifiers set on a container now apply to its whole subtree — SwiftUI's environment semantics for .font, .foregroundColor, and .disabled. Previously these only had an effect when attached directly to a Text or Button; on a VStack they were silently ignored.

How it works

Pure interpreter change (the modifiers already emit on any view from earlier tiers). Modeled the same way Compose models its own text environment — CompositionLocals:

• LocalInheritedFontSize / LocalInheritedFontWeight / LocalInheritedColor / LocalInheritedDisabled
• Render(node) folds the node's own font/foregroundColor/disabled modifiers into these before rendering its subtree (right alongside the existing animation-spec provider).
• RenderText starts from the inherited values; its own modifiers override them. Button is disabled when either its own or an inherited .disabled(true) is in scope.

Explicit-wins is automatic: a child's own .font overrides the inherited one.

Verification

• Desktop Kotlin compiles; emulator (new Styling screen): three Texts inheriting a container .font(.title); two inheriting .foregroundColor(.blue); a child .font(.caption) overriding an inherited title; combined headline+purple; and a .disabled(true) container whose buttons are dimmed and non-interactive (tap count stays 0)

Deferred

Inherited .disabled fully disables Button and visually dims the subtree (container alpha), but does not yet set enabled = false on Toggle/Slider/TextField. .italic/.lineLimit/.multilineTextAlignment remain Text-local (not propagated).