Adds banner targets to close session view and post-purchase screen

[Profilist]

Background

This PR adds two new banner extention targets for POS UI Extensions as part of the Extensible Cash Management on POS project:

• pos.purchase.post.banner.render - Allows rendering a banner at the top of the post-purchase screen
• pos.cash-tracking-session-float.banner.render - Allows rendering a banner during the end cash tracking session flow on the Set Desired Float screen

Solution

Added the following:

1. New target type definitions in ExtensionTargetType.ts and TargetLink.ts
2. Documentation files for both new targets
3. Example implementations in both TypeScript and React
4. Updated the ExtensionTargets interface to include the new banner targets with appropriate API types

🎩

• Verified the documentation renders correctly
• Tested the example implementations with both TypeScript and React approaches
• Confirmed the new targets are properly typed in the extension API

Checklist

• I have 🎩'd these changes
• I have updated relevant documentation

[Profilist]

• Adds banner targets to close session view and post-purchase screen #3131 👈 (View in Graphite)
• unstable

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[github-actions]

We detected some changes in packages/*/package.json or packages/*/src, and there are no updates in the .changeset directory. If the changes are user-facing and should cause a version bump, run yarn changeset to track your changes and include them in the next release CHANGELOG. If you are making simple updates to repo configuration, examples, or documentation, you do not need to add a changeset.

[github-actions]

📝 POS Version Documentation Reminder

We detected changes in packages/*/src/surfaces/point-of-sale, but there are no updates to the POS versions documentation.

If these changes are user-facing and should be documented in the version changelog, please update:
packages/ui-extensions/docs/surfaces/point-of-sale/staticPages/pages/versions.doc.ts

If you are making internal changes that don't affect the public API, you can ignore this reminder.