Add CSS isolation support to SVG Frame

[arnavsharma990]

Adds support for the CSS isolation property on Frame.

• Introduces a minimal Isolation sealed trait (Auto, Isolate)
• Adds optional isolation field to Frame
• Emits isolation in svgTag only when set
• No behavior changes when isolation is not specified

Closes #228

[arnavsharma990]

Note: The issue description(#228 ) mentions that an ideal solution could allow arbitrary CSS styles on Frame, potentially reusing ScalaTags.

This PR intentionally focuses only on supporting the isolation property to keep the change minimal and aligned with the current issue scope. If desired, I’d be happy to explore a more general style mechanism in a follow up PR.

[Copilot]

Pull request overview

Adds support for the CSS isolation property on the SVG root element via Frame, allowing callers to control blending/stacking behavior of rendered SVG output.

Changes:

• Introduces doodle.svg.effect.Isolation ADT (Auto, Isolate) with toCSS rendering.
• Extends doodle.svg.effect.Frame with an optional isolation field and a withIsolation builder.
• Updates SVG root tag rendering to emit isolation: ... in the inline style when configured.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
svg/shared/src/main/scala/doodle/svg/effect/Isolation.scala	Adds an ADT representing CSS isolation values and CSS serialization.
svg/shared/src/main/scala/doodle/svg/effect/Frame.scala	Adds optional isolation to the public Frame API plus a builder method.
svg/shared/src/main/scala/doodle/svg/algebra/Svg.scala	Appends isolation into the generated root <svg> style attribute.

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