* fix: Tiptap Media Picker: Skip media picker modal when editing existing images
Fixes the media picker workflow to match v13 behavior where clicking
an existing image directly opens the alt text/caption editor instead
of forcing users to re-select the same image from the media library.
Also fixes caption text extraction to properly read from the figcaption
node using Tiptap's NodeSelection API instead of unreliable attribute-based
approach.
Changes:
- Skip media picker when currentMediaUdi exists (lines 77-92)
- Extract caption from NodeSelection.node using descendants() (lines 55-73)
- Add NodeSelection export to tiptap externals for proper typing
* Refactor: Extract nested logic from media picker execute method
Reduces cyclomatic complexity from 15 to 1 by extracting conditional
logic into focused private helper methods. Addresses CodeScene warnings
for complex method and nested conditionals (bumpy road smell).
Created helper methods:
- #extractMediaUdi, #extractCaption, #findFigcaptionText
- #getMediaGuid, #updateImageWithMetadata
No functional changes - improves maintainability and testability.
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