RemixSpinner and RemixProgress need optional semantics

[leoafarias]

Summary

RemixSpinner and RemixProgress have no first-class way to expose an accessible name or progress value. The generated Fortal wrappers therefore cannot forward one.

Found while validating #80 at b16636b017f3c8832d8f27f316cc24c0ad92ce8a, including the final generator/API decisions from stacked PR #84.

Evidence

• RemixSpinner renders a visual CustomPaint and accepts only style inputs.
• RemixProgress requires a determinate value but renders only visual boxes.
• Neither source tree nor its component tests contains a semantic label/value contract.

Flutter's standard ProgressIndicator exposes semanticsLabel and semanticsValue; its determinate implementation can derive a percentage when an explicit value string is absent.

Decorative-by-default behavior is reasonable. The gap is that a consumer cannot opt into a named/status primitive through the Remix/Fortal API without wrapping the component and reimplementing its semantics ownership.

Expected

Consumers can choose:

• a decorative spinner/progress indicator with no independent node;
• a nondecorative indicator with one accessible name and appropriate value/state.

Suggested direction

• Add optional semantic label/value inputs to the base Remix widgets.
• Let the final @MixWidget Fortal wrappers forward those target parameters automatically.
• For determinate progress, expose the normalized value in the same node.
• Keep spinner announcements opt-in; animation alone must not repeatedly announce.

Acceptance criteria

• Null semantic inputs keep the indicators decorative.
• A labelled spinner exposes one noninteractive status/progress node.
• A labelled determinate progress bar exposes one name and its current normalized value.
• Updating progress changes the existing node rather than adding duplicates.
• Generated Fortal wrappers forward the final API without handwritten drift.
• Headless semantics tests cover decorative, labelled, and updated states.

Scope

This does not request indeterminate RemixProgress; PR #80 explicitly defers that visual/API capability. It only covers semantics for the indicator modes that already exist.

[leoafarias]

Resolved by #80 and included in merge commit 40704eb. The merged PR includes the implementation and verification for this issue. Closing as completed.