[Precursor] Add Precursor Dev Docs for Launch

[marinaelmore]

Summary

Add dev docs for Precursor launch

Screenshots (optional)

Documentation checklist

• Is there a changelog entry (guidelines)? If you don't add one for something awesome and new (however small) — how will our customers find out? Changelogs are automatically posted to RSS feeds, the Discord, and X.
• The change adheres to the documentation style guide.
• If a larger change - such as adding a new page- an issue has been opened in relation to any incorrect or out of date information that this PR fixes.
• Files which have changed name or location have been allocated redirects.

[cloudflare-docs-bot]

Review

💡 3 suggestions found in commit 10d2f5c.

Code Review

This code review is in beta and may not always be helpful — use your judgment.

_{No code review issues found.}

Conventions

Checks PR title, description, and redirect checklist.

_{No convention issues found.}

Style Guide Review

Suggestions (3)

File	Issue
cloudflare-challenges/precursor.mdx line 42	Bulleted list has fewer than three items — Only two bullet items (Minimize Friction and Maximize Security) list the Precursor modes Fix: Consider rewriting the two mode descriptions as prose instead of a two-item bulleted list
cloudflare-challenges/precursor.mdx line 90	Passive voice — Precursor is tightly integrated with cf_clearance uses passive voice Fix: Rewrite in active voice, for example: Precursor integrates tightly with cf_clearance
cloudflare-challenges/concepts/clearance.mdx line 51	Passive voice — Sentence uses passive voice ('Precursor clearance is continuously re-evaluated', 'is updated dynamically') and could be more direct in active voice. Fix: Rewrite in active voice, for example: 'Precursor continuously re-evaluates clearance throughout a visitor's session...'

Redirects

_{No missing redirect entries found.}

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[marinaelmore]

/review