fix(app): repair web manifest and OAuth errors; fix Windows typings

[Observer-GGboy]

What does this PR do?

• Fix invalid site.webmanifest that caused a manifest parse error in the web UI.
• Improve OAuth error visibility in the connect dialog and include response details for token exchange failures.
• Replace Windows placeholder custom-elements.d.ts files with actual typings in app/enterprise packages.

How did you verify your code works?

• bun turbo typecheck Fixes #8812

[github-actions[bot]]

Hey! Your PR title Fix web manifest, OAuth error visibility, and Windows custom element typings doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions[bot]]

The following comment was made by an LLM, it may be inaccurate:

No duplicate PRs found.

[github-actions[bot]]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[adamdotdevin]

@Observer-GGboy why the change to the codex plugin?

[adamdotdevin]

@Observer-GGboy if you can revert the changes to codex.ts then i'll merge