fix: improving handling of unbounded width in ResponsiveRow

[ndonkoHenri]

Fix #1951

Test code

import flet as ft


def main(page: ft.Page):
    page.add(
        ft.Row(
            controls=[
                ft.ResponsiveRow(
                    # expand=True,
                    controls=[
                        ft.Text("Item 1"),
                        ft.Text("Item 2"),
                    ],
                )
            ]
        )
    )


ft.run(main)

Summary by Sourcery

Handle unbounded layout constraints more robustly and improve visual regression coverage for affected controls.

New Features:

• Display an explicit error control when a ResponsiveRow is built with unbounded width to guide developers toward supported layouts.

Bug Fixes:

• Require an icon for NavigationRailDestination to prevent invalid configurations that could lead to runtime issues.

Enhancements:

• Adjust async test fixtures to use function-scoped Flet test apps, ensuring each test runs with an isolated app instance.

Tests:

• Add screenshot tests for ResponsiveRow with unbounded width and various controls (PageView, Tabs/TabBarView, NavigationRail, Pagelet) under unbounded height scenarios to guard against regressions.

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Pull request overview

Improves handling of layout constraint edge-cases (notably unbounded constraints) by surfacing clear runtime errors in the Flutter client and adding golden/integration coverage for these scenarios.

Changes:

• Add an explicit unbounded-width guard to ResponsiveRow (Flutter) that renders an ErrorControl with guidance.
• Add/extend integration + golden tests for unbounded constraint cases (ResponsiveRow width; PageView/Pagelet/NavigationRail/TabBarView height).
• Adjust Python NavigationRailDestination.icon typing/requiredness and bump client/pubspec.lock to match packages/flet version.

Reviewed changes

Copilot reviewed 7 out of 13 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
packages/flet/lib/src/controls/responsive_row.dart	Detects unbounded width and renders a helpful ErrorControl instead of mis-layout.
sdk/python/packages/flet/integration_tests/controls/core/test_responsive_row.py	Adds screenshot test coverage for unbounded-width ResponsiveRow.
sdk/python/packages/flet/integration_tests/controls/core/test_page_view.py	Adds screenshot test for unbounded-height PageView.
sdk/python/packages/flet/integration_tests/controls/core/test_pagelet.py	Adds screenshot test for unbounded-height Pagelet.
sdk/python/packages/flet/integration_tests/controls/material/test_navigation_rail.py	Adds screenshot test for unbounded-height NavigationRail.
sdk/python/packages/flet/integration_tests/controls/material/test_tabs.py	Adds screenshot test for unbounded-height TabBarView.
sdk/python/packages/flet/src/flet/controls/material/navigation_rail.py	Changes NavigationRailDestination.icon to be required in the Python API.
sdk/python/packages/flet/integration_tests/**/golden/**.png	New golden images for the added constraint-error scenarios.
client/pubspec.lock	Updates locked versions (including flet 0.83.1) consistent with the repo package version.

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