feat: add stacSliverSafeArea widget, parser,example and documentation

[akhil-ge0rge]

Description

This PR introduces support for stacSliverSafeArea by adding a new widget model and its corresponding parser.

Related Issues

Closes #420

Type of Change

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to change)
• Code refactor
• Build configuration change
• Documentation
• Chore

Summary by CodeRabbit

• New Features

  • Added SliverSafeArea widget support for sliver-based layouts (configurable insets).

• Documentation

  • New SliverSafeArea doc page with properties, examples, and links to official docs.

• Examples

  • New gallery entry and example demonstrating SliverSafeArea usage.

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[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds a StacSliverSafeArea widget: model, JSON (de)serialization, parser, widget-type registration, documentation, and a gallery example; it also registers the parser in StacService and exports the parser and widget from their barrels.

Changes

Cohort / File(s)	Summary
Core Widget Model packages/stac_core/lib/widgets/sliver_safe_area/stac_sliver_safe_area.dart, packages/stac_core/lib/widgets/sliver_safe_area/stac_sliver_safe_area.g.dart, packages/stac_core/lib/widgets/widgets.dart, packages/stac_core/lib/foundation/specifications/widget_type.dart	Added StacSliverSafeArea model with fields (left, top, right, bottom, minimum, sliver), JSON (de)serialization, exported from widgets barrel, and added sliverSafeArea to WidgetType enum.
Parser Implementation & Registration packages/stac/lib/src/parsers/widgets/stac_sliver_safe_area/stac_sliver_safe_area_parser.dart, packages/stac/lib/src/parsers/widgets/widgets.dart, packages/stac/lib/src/framework/stac_service.dart	Added StacSliverSafeAreaParser (null-tolerant defaults; fallback inner sliver), exported parser in parsers barrel (duplicate export present), and registered parser in StacService parser list.
Documentation docs/docs.json, docs/widgets/sliver_safe_area.mdx	Added docs entry under Widgets → Interactive Widgets and new MDX page describing SliverSafeArea with properties and example.
Gallery Examples examples/stac_gallery/assets/json/home_screen.json, examples/stac_gallery/assets/json/sliver_safe_area_example.json	Added gallery list item and JSON example demonstrating a sliverSafeArea wrapping a sliverToBoxAdapter with text content.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Suggested labels

feature

Suggested reviewers

• divyanshub024
• Potatomonsta

Poem

🐰 A safe area for slivers, snug and neat,
Padding the edges where scrolls and slivers meet.
A tiny parser hops in to play,
Turning JSON to widgets along the way.
Hooray for safe scrolls — a rabbit's little treat!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and accurately describes the main change: adding a StacSliverSafeArea widget along with its parser, example, and documentation.
Linked Issues check	✅ Passed	The PR implements StacSliverSafeArea [#420], the core requirement, with widget model, parser, documentation, and examples.
Out of Scope Changes check	✅ Passed	All changes directly relate to adding SliverSafeArea support: widget model, parser, documentation, examples, and integration into the framework.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In
`@packages/stac/lib/src/parsers/widgets/stac_sliver_safe_area/stac_sliver_safe_area_parser.dart`:
- Line 19: The current fallback for model.sliver.parse(context) uses
SizedBox.shrink() which is not a sliver and will crash SliverSafeArea; either
remove the fallback (since model.sliver is non-nullable) or replace it with a
sliver-compatible fallback such as wrapping the box in a SliverToBoxAdapter;
update the expression using model.sliver.parse(context) and ensure
SliverSafeArea receives a RenderSliver-compatible child (refer to the sliver
variable and the SliverSafeArea usage).