The "Improve debugging with better Angular error messages" and "Launch advanced compiler diagnostics" cards on the roadmap page pointed to reference/errors and reference/extended-diagnostics, which are not routed on angular.dev. The published routes are /errors and /extended-diagnostics. Also drop an inconsistent leading slash from the Signal Forms card href to match the rest of the file.

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular/blob/main/contributing-docs/commit-message-guidelines.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• angular.dev application / infrastructure changes
• Other... Please describe:

What is the current behavior?

Two cards on https://angular.dev/roadmap 404:

• "Improve debugging with better Angular error messages" → reference/errors
• "Launch advanced compiler diagnostics" → reference/extended-diagnostics

The published routes are /errors and /extended-diagnostics.

What is the new behavior?

Cards point to the real routes. Also removes a stray leading slash from one href so all cards in the file use the same format.

Does this PR introduce a breaking change?

• Yes
• No