fix: rename clipboardTextSerializer extension to avoid duplicate with tiptap core

[devin-ai-integration]

Summary

Fixes the tiptap warning: [tiptap warn]: Duplicate extension names found: ['clipboardTextSerializer']. This can lead to issues.

The warning appeared because our custom ClipboardTextSerializer extension had the same name as a built-in tiptap v3 core extension (referenced in tiptap docs as coreExtensionOptions.clipboardTextSerializer). This PR renames both the extension name and its ProseMirror PluginKey to hyprnoteClipboardTextSerializer to avoid the collision.

The clipboardTextSerializer prop in ProseMirror's props object is unchanged since that's the actual prop name, not our extension's identifier.

Review & Testing Checklist for Human

• Open a session tab and verify the duplicate extension warning no longer appears in the console
• Test copy/paste functionality in the editor - select all content and paste into a text field to verify the custom clipboard serializer still works (should convert to markdown when copying entire document)

Notes

Link to Devin run: https://app.devin.ai/sessions/291c297bf1734505bc70a43a9ed52980
Requested by: @yujonglee (yujonglee.dev@gmail.com)

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR that start with 'DevinAI' or '@devin'.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring

[netlify]

✅ Deploy Preview for hyprnote ready!

Name	Link
🔨 Latest commit	b193029
🔍 Latest deploy log	https://app.netlify.com/projects/hyprnote/deploys/69539e3d61d2b100081f0d39
😎 Deploy Preview	https://deploy-preview-2669--hyprnote.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[netlify]

✅ Deploy Preview for howto-fix-macos-audio-selection canceled.

Name	Link
🔨 Latest commit	b193029
🔍 Latest deploy log	https://app.netlify.com/projects/howto-fix-macos-audio-selection/deploys/69539e3d33c2840008681780

[netlify]

✅ Deploy Preview for hyprnote-storybook ready!

Name	Link
🔨 Latest commit	b193029
🔍 Latest deploy log	https://app.netlify.com/projects/hyprnote-storybook/deploys/69539e3de0d5e7000833679f
😎 Deploy Preview	https://deploy-preview-2669--hyprnote-storybook.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.