feat: step item with anchor links

[pqoqubbw]

Summary

Test Plan

---

Note

Medium Risk
Touches interactive UI behavior and browser APIs (clipboard + hash/scroll handling), which can be sensitive to SSR and event-handling edge cases, but is scoped to the Steps component.

Overview
Adds optional deep-linking to Steps.Item via new id/noAnchor props, showing a hover-only link icon on the step number/title and copying an encoded #id URL to the clipboard (and updating window.location.hash) when clicked.

Introduces callbacks (onRegisterHeading/onUnregisterHeading, scrollElementIntoView, onCopyAnchorLink) and react-use-rect measurement to support registering headings and auto-scrolling to a step on initial load when the page hash matches. Storybook gains a WithAnchorLinks example demonstrating enabled/disabled anchors.

^{Written by Cursor Bugbot for commit 6ab4d5a. This will update automatically on new commits. Configure here.}

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{Bugbot Autofix is OFF. To automatically fix reported issues with Cloud Agents, enable Autofix in the Cursor dashboard.}