Feature/add stacking layout support

[dasvh]

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[Copilot]

Pull Request Overview

This PR implements stacking (vertical) layout support for the task selector UI, allowing users to stack the task list above the preview window as an alternative to the default side-by-side horizontal layout.

• Adds vertical layout option with height_ratio configuration for controlling list vs preview height distribution
• Implements layout toggling functionality via :TaskToggleLayout command with session persistence
• Adds comprehensive UI constants and validation for both horizontal and vertical layouts

Reviewed Changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/taskfile/ui_spec.lua	Extensive test coverage for vertical layout behavior, window sizing, and layout toggling
tests/taskfile/setup_spec.lua	Validation tests for height_ratio configuration and layout option parsing
tests/minimal_init.lua	Test environment improvements with better dependency management
plugin/taskfile.lua	New TaskToggleLayout command implementation
lua/taskfile/utils.lua	UI constants consolidation and layout normalization utilities
lua/taskfile/ui.lua	Core vertical layout implementation and window positioning logic
lua/taskfile/core.lua	Configuration schema updates and improved task execution handling
demo/demo.tape	Demo updates showcasing layout toggle functionality
Taskfile.yml	Added format task for code formatting
README.md	Documentation updates for new layout features

Comments suppressed due to low confidence (2)

lua/taskfile/core.lua:1

• [nitpick] The variable name total_weight is misleading as it represents width, not weight. It should be renamed to total_width for consistency with other similar variables in the codebase.

---@Class core

lua/taskfile/ui.lua:1

• The magic number 2 should be replaced with the ui.const.WINDOW_GAP constant that is already defined and used elsewhere in the file.

--@Class ui

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