docs(readme): add Wireframe Visual Feedback Loop row

Addresses @mnriem's follow-up: the README extension table also
needs an entry, not just the catalog JSON. Slots in alphabetically
between "What-if Analysis" and "Worktree Isolation" with category
`visibility` and Read+Write effect (since sign-off writes the
approved wireframe paths into spec.md).

Author: TurtleWolfe

README.md

@@ -257,6 +257,7 @@ The following community-contributed extensions are available in [`catalog.commun
 | Verify Extension | Post-implementation quality gate that validates implemented code against specification artifacts | `code` | Read-only | [spec-kit-verify](https://github.com/ismaelJimenez/spec-kit-verify) |
 | Verify Tasks Extension | Detect phantom completions: tasks marked [X] in tasks.md with no real implementation | `code` | Read-only | [spec-kit-verify-tasks](https://github.com/datastone-inc/spec-kit-verify-tasks) |
 | What-if Analysis | Preview the downstream impact (complexity, effort, tasks, risks) of requirement changes before committing to them | `visibility` | Read-only | [spec-kit-whatif](https://github.com/DevAbdullah90/spec-kit-whatif) |
+| Wireframe Visual Feedback Loop | SVG wireframe generation, review, and sign-off for spec-driven development. Approved wireframes become spec constraints honored by /plan, /tasks, and /implement | `visibility` | Read+Write | [spec-kit-extension-wireframe](https://github.com/TortoiseWolfe/spec-kit-extension-wireframe) |
 | Worktree Isolation | Spawn isolated git worktrees for parallel feature development without checkout switching | `process` | Read+Write | [spec-kit-worktree](https://github.com/Quratulain-bilal/spec-kit-worktree) |
 | Worktrees | Default-on worktree isolation for parallel agents — sibling or nested layout | `process` | Read+Write | [spec-kit-worktree-parallel](https://github.com/dango85/spec-kit-worktree-parallel) |