#16413 fix(plugins): open tools after MCP setup completes

Description

Open the saved plugin's Tools tab after MCP setup succeeds, including OAuth connections with an existing valid grant. Setup previously returned to Configuration, which made successful authentication appear to restart setup.

Separate authentication error notices from their recovery buttons with consistent spacing. This includes the Use your own OAuth client action after automatic registration fails.

This PR builds on #16419. It uses the existing detail route with tab=tools and preserves the stack's staged validation and name-first focus. The stack includes the shared Chat update fix from main. The temporary exclusive scheduling workaround is removed.

How Has This Been Tested?

• Passed all 174 tests across the affected UI, MCP service, and translation suites after rebasing.
• Verified completed setup selects Tools without repeating discovery. Legacy OAuth return coverage still selects Tools and discovers once.
• Passed changed-file checks for TypeScript, coverage, formatting, lint, secrets, and feature-map integrity.
• Playwright CI will rerun on this stacked revision, including the personal-key tests under normal scheduling.
• The registration-error recovery test passes after the spacing fix.
• Live external provider consent was not tested.

Additional Options

• [Optional] Please cherry-pick this PR to the latest release version.

Summary by CodeRabbit

• New Features

  • MCP setup completion now opens the plugin detail page directly on the Tools tab.
  • OAuth returns and existing authenticated connections open the Tools tab, with legacy OAuth returns continuing to support tool discovery.
  • Direct navigation to the Tools tab is supported without triggering tool discovery.

• Bug Fixes

  • Improved the MCP authentication error layout while preserving recovery options for registration and discovery failures.