feat: add stacSliverToBoxAdapter widget, parser,example and documentation

[akhil-ge0rge]

Description

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

Related Issues

Closes #422

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 SliverToBoxAdapter widget to support embedding box widgets inside sliver-based layouts.

• Documentation

  • Added a new docs page detailing properties, usage patterns, and examples.

• Examples

  • Added an interactive gallery entry and a runnable example demonstrating SliverToBoxAdapter usage.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Adds first-class support for SliverToBoxAdapter: a StacSliverToBoxAdapter model with JSON (de)serialization, a parser that renders a Flutter SliverToBoxAdapter, registration of the parser in the framework, WidgetType enum variant, exports, docs, and example gallery assets.

Changes

Cohort / File(s)	Summary
Documentation docs/docs.json, docs/widgets/sliver_to_box_adapter.mdx	New docs entry and page for SliverToBoxAdapter under Widgets → Layout Widgets; includes props table and example JSON.
Example Assets examples/stac_gallery/assets/json/home_screen.json, examples/stac_gallery/assets/json/sliver_to_box_adapter_example.json	Added gallery menu item and example JSON demonstrating a CustomScrollView → SliverPadding → SliverToBoxAdapter with a centered container.
Core Model packages/stac_core/lib/widgets/sliver_to_box_adapter/stac_sliver_to_box_adapter.dart, packages/stac_core/lib/widgets/sliver_to_box_adapter/stac_sliver_to_box_adapter.g.dart	New StacSliverToBoxAdapter JsonSerializable model with optional child and generated (de)serializers. Review JSON shape and generated code.
Widget Type & Exports packages/stac_core/lib/foundation/specifications/widget_type.dart, packages/stac_core/lib/widgets/widgets.dart	Added sliverToBoxAdapter enum value and exported the new model from the widgets barrel.
Parser Implementation & Exports packages/stac/lib/src/parsers/widgets/stac_sliver_to_box_adapter/stac_sliver_to_box_adapter_parser.dart, packages/stac/lib/src/parsers/widgets/widgets.dart	New StacSliverToBoxAdapterParser mapping JSON→model→SliverToBoxAdapter widget; exported from parsers barrel. Check parser type string matches enum-derived name.
Framework Registration packages/stac/lib/src/framework/stac_service.dart	Registered StacSliverToBoxAdapterParser in the service's parsers list.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• feat: Introduce StacError and StacErrorWidget for enhanced error handling #364: Modifies stac_service.dart; related because both alter parser registration in the framework.
• feat: Introduce stacBadge widget and parser with example JSON #388: Adds new widget support across WidgetType, parsers, core widgets, and examples; strongly related in scope and approach.

Suggested reviewers

• divyanshub024
• Potatomonsta

Poem

🐰 A sliver cradles a tiny box so snug,
JSON whispers, the parser gives a hug,
Model and docs hop in, all set to play,
From text to widget — a bright new display! ✨

🚥 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 accurately describes the main changes: addition of stacSliverToBoxAdapter widget, parser, example, and documentation.
Linked Issues check	✅ Passed	The PR successfully implements StacSliverToBoxAdapter as a StacWidget, fulfilling the core requirement of issue #422.
Out of Scope Changes check	✅ Passed	All changes are directly related to implementing SliverToBoxAdapter support: widget model, parser, type registration, exports, documentation, and example.
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: 2

🤖 Fix all issues with AI agents

In `@docs/widgets/sliver_to_box_adapter.mdx`:
- Around line 6-8: Update the prose describing the widget to hyphenate the
compound adjective: replace occurrences of "sliver to box adapter" with
"sliver-to-box-adapter" in the sentence that mentions "The Stac
SliverToBoxAdapter allows you to build a Flutter sliver to box adapter widget
using JSON." Ensure the phrase "sliver-to-box-adapter widget" appears
consistently (e.g., in the line referencing the official documentation) and keep
the class name "SliverToBoxAdapter" unchanged.

In `@packages/stac_core/lib/foundation/specifications/widget_type.dart`:
- Around line 210-211: The doc comment for the enum value sliverToBoxAdapter is
incorrect (it says "Sliver app bar widget"); update the comment above the
sliverToBoxAdapter enum member in widget_type.dart to accurately describe that
it represents a SliverToBoxAdapter widget (e.g., "SliverToBoxAdapter widget" or
similar). Ensure the updated comment is concise and matches the naming/style of
other enum docs in the same file.

[akhil-ge0rge]

Hi @divyanshub024 , @Potatomonsta 👋,
Please take a look. Thanks!