chore(duo-agent-platform-v2): clean up feature flag and import types

Juhee Leerequested to merge
2837/gate-DAP-UI-V2-behind-experiment-features-setting-remove-ff into main

Description

Now that UI V2 is gated behind the experiment/beta features setting, the dedicated flag is no longer needed and causes confusion if it's not set. The new UI becomes the default (opt-out) once experiment features are enabled, and the user's enable/disable choice survives window reloads.

  • Removes the client-side duoAgentPlatformNext feature flag that gated the Duo Agent Platform UI V2, replacing it with a user preference persisted in globalState.
  • Switches the experiment/beta features notification handling to use the strongly-typed constants exported from @gitlab-org/gitlab-lsp.

Follow-up to !3298 (merged)

Related Issues

Issue #2837

How has this been tested?

  • If src/browser or src/common has been modified, please consider interoperability with the Web IDE. See Running the Extension in WebIDE.
  • Consider an end-to-end test for significant new features that aren't covered by integration tests.
  1. Run the extension locally
  2. With experimental settings on, new UI should be present by default with a toggle button.
  3. Click toggle button to Class layout.
  4. Reload and verify the choice is persisted
  5. Turn off experimental settings and old UI shows up with no toggle button

Screenshots (if appropriate)

What CHANGELOG entry will this MR create?

  • fix: Bug fix fixes - a user-facing issue in production - included in changelog
  • feature: New feature - a user-facing change which adds functionality - included in changelog
  • BREAKING CHANGE: (fix or feature that would cause existing functionality to change) - should bump major version, mentioned in the changelog
  • None - other non-user-facing changes

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