#4113 feat(desktop): remove skip-all onboarding affordance

Summary

• Remove the chrome-level "Skip onboarding" button from OnboardingProgress and drop the skipAll action (plus its skipped_all analytics event) from the onboarding store
• Per-step "Skip for now" links via markSkipped() are unchanged — users can still skip individual steps

Test plan

• Launch desktop in v2 onboarding, confirm no "Skip onboarding" button appears in the top chrome
• Each step's "Skip for now" link still works and advances the flow
• Required steps (providers, project) still gate /welcome until completed or skipped
• bun run lint and bun run typecheck pass

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Summary by cubic

Removed the global “Skip onboarding,” stacked Claude Code and Codex with per‑provider Connect and inline Reconfigure/Cancel, and standardized bottom Continue/“Skip for now” across steps (incl. gh-cli and adopt-worktrees). Added OpenAI OAuth localhost loopback that auto‑completes via renderer polling and refreshed connect headers with the Superset brand glyph in 44×44 tiles matching squared provider logos.

• New Features

  • Auto-capture OpenAI OAuth callback via localhost; the renderer polls consumeOpenAIOAuthCallback to complete auth and routes back to /setup/providers. Loopback stops on cancel/complete and falls back if the port can’t bind.
  • Select worktrees to import in adopt-worktrees via checkboxes (with Select all); new workspaces.importExternalWorktrees accepts paths, and selectExternalWorktreesForImport is used by both the query and import to keep the UI in sync (with tests).
  • Use the Superset brand glyph in 44×44 rounded tiles and align Codex/Claude tile shapes/sizes for visual consistency.

• Bug Fixes

  • Loopback binds to the redirect_uri host (supports localhost, 127.0.0.1, and ::1) to prevent bind failures on IPv6 systems.
  • Fixed reconnect flows getting stuck on OAuth subroutes by driving navigation from onAuthStateChange back to /setup/providers.

Summary by CodeRabbit

• Chores

  • Removed the global "Skip onboarding" action—onboarding must be completed step-by-step; Back navigation still works.

• New Features

  • Per-step "Skip for now" options added on several setup screens (worktrees, GH CLI, etc.).
  • Provider setup redesigned to show provider sections concurrently with clearer connect/configure actions.
  • Added an OpenAI OAuth loopback flow to simplify OAuth sign-in via a local callback.
  • Hook callback support to notify UI after OpenAI auth state changes.
  • New API endpoint to consume OpenAI OAuth callbacks.

• Refactor

  • Streamlined onboarding controls and layout for more consistent step rendering.