feat: add Pennant flags for staged desktop UI rollout

[ibourgeois]

Summary

• add Laravel Pennant with desktop-scoped UI rollout features and published config/migration
• add a shared DesktopUi helper, staged shell gate, and tests for naming/defaults/activation
• sync Boost agent metadata and Pennant skill docs with the new dependency

Testing

• vendor/bin/pint --dirty --format agent
• php artisan test --compact tests/Feature/DesktopUiFeatureFlagTest.php tests/Feature/DesktopShellTest.php

Closes #99

[Copilot]

Pull request overview

Adds Laravel Pennant-based feature flags to support a staged rollout of desktop UI surfaces in Katra, establishing conventions and initial gated UI content for the desktop shell.

Changes:

• Introduces Pennant (config + migration) and desktop-scoped UI rollout feature classes (ui.desktop.*).
• Adds App\Support\Features\DesktopUi helper and wires a first gated “Workspace navigation pilot” surface into the home controller + welcome view.
• Adds Pest feature tests and updates contributor/agent docs + Boost skills metadata for Pennant.

Reviewed changes

Copilot reviewed 24 out of 25 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
composer.json	Adds laravel/pennant dependency.
composer.lock	Locks Pennant and updates dependency graph.
config/pennant.php	Adds Pennant store configuration (array/database).
database/migrations/2026_03_21_004800_create_features_table.php	Adds Pennant features table migration.
app/Features/Desktop/*.php	Defines initial desktop UI rollout flags with ui.desktop.* naming.
app/Support/Features/DesktopUi.php	Central helper for scope, feature list, and flag checks.
app/Http/Controllers/HomeController.php	Resolves and passes desktop UI flags to the welcome view.
resources/views/welcome.blade.php	Conditionally shows “Workspace navigation pilot” UI section.
tests/Feature/DesktopUiFeatureFlagTest.php	Tests naming convention, defaults, and activation behavior.
tests/Feature/DesktopShellTest.php	Ensures pilot UI is hidden by default in shell.
CONTRIBUTING.md	Documents feature-flag conventions for desktop UI rollout.
boost.json	Enables Pennant skill for agent workflows.
AGENTS.md / CLAUDE.md / GEMINI.md	Syncs agent metadata to include Pennant.
.junie/.github/.cursor/.claude/.agents/skills/pennant-development/SKILL.md	Adds Pennant skill documentation across tooling directories.

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