[rfw] Coerce numeric values in core Text widget

[ciriousjoker]

This PR fixes numeric rendering in RFW core Text widgets.

Before:

• Text(text: data.value) rendered empty when data.value was int or double.
• Text(text: [data.left, " / ", data.right]) only rendered string segments.

After:

• int and double values are stringified in both code paths:
  • direct Text(text: data.value)
  • list segments Text(text: [...])
• Other types are unchanged (no bool/object coercion).

Fixes

• Fixes RemoteFlutterWidgets: Text doesn't render numbers flutter#183034

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I followed the version and CHANGELOG instructions, using semantic versioning and the repository CHANGELOG style, or I have commented below to indicate which documented exception this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

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Footnotes

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[gemini-code-assist]

Code Review

This pull request correctly addresses an issue where numeric values were not rendered in Text widgets, by implementing proper coercion of int and double values to strings in core_widgets.dart. A security audit confirmed that type coercion is safe, data flow is controlled, and no security vulnerabilities were identified. The accompanying test cases in core_widgets_test.dart are thorough, and I've provided a suggestion to improve the conciseness of the implementation for list-based text segments.