Enable AI Assistant and remove its feature flag

[Mbeaulne]

Description

The AI Assistant is ready to be enabled for all users, so this removes the ai-assistant feature flag and its conditional code paths.

The AI Assistant window is now always registered in the V2 editor and Run View. AI Configuration is always available in Settings, and the model selector is shown whenever an AI provider is configured. Tests that covered the retired flag states have been simplified accordingly.

Related Issue and Pull requests

None.

Type of Change

• Improvement
• Cleanup/Refactor

Checklist

• I have tested this does not break current pipelines / runs functionality
• I have tested the changes on staging

Screenshots (if applicable)

Not applicable.

Test Instructions

1. Open Settings → Beta Features and confirm AI Assistant is no longer listed.
2. Open the V2 editor and confirm Sidekick is available.
3. Open a pipeline run and confirm AI Assistant is available.
4. Open Settings and confirm AI Configuration is always visible and accessible.
5. Configure an AI provider and confirm the AI model selector appears in the application header.

Run the focused tests:

pnpm exec vitest run src/components/layout/AiModelQuickSelect.test.tsx src/routes/v2/pages/RunView/hooks/runWindowVisibilityPersistence.test.tsx

Additional Comments

Existing ai-assistant values in local storage are ignored after this change.

[github-actions]

🎩 Preview

A preview build has been created at: remove-ai-assistant-feature-flag/92f6b3e