fix: TemplatingEditor paste action override current content

[AlekseyManetov]

Related to camunda/camunda-modeler#5948

Proposed Changes

The bug was cause by wrong paste behavior in FeelTemplatingEntry. The pasteHandler in Feel.js is registered on a container <div> and catches paste events from all child elements via event bubbling. It accesses event.target.value and event.target.selectionStart — properties that only exist on <input> elements.

When FeelTemplatingEntry renders a CodeMirror editor (contenteditable <div>), event.target.value is undefined. Since !undefined evaluates to true, the handler always treats the field as empty, replaces the entire content with the pasted text, and calls preventDefault() — blocking CodeMirror's native paste.

Before:

Screen.Recording.2026-05-29.at.15.59.04.mov

After:

Screen.Recording.2026-05-29.at.15.58.24.mov

Checklist

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[Copilot]

Pull request overview

This PR fixes a paste-handling bug where the generic FEEL paste handler (registered on a container) incorrectly intercepts paste events coming from CodeMirror-based templating editors, causing pasted content to overwrite the entire editor content instead of inserting at the cursor.

Changes:

• Update the FEEL paste handler to ignore non-<input> paste targets (to avoid interfering with CodeMirror/contenteditable editors).
• Add a regression test ensuring FeelTemplatingEntry paste does not overwrite existing content.
• Extend the example app setup to include a FeelTemplatingEntry to exercise templating behavior.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/components/entries/FEEL/Feel.js	Adjust paste handler target handling to avoid overriding CodeMirror paste behavior.
test/spec/components/Feel.spec.js	Add regression test for pasting into FeelTemplatingEntry (CodeMirror).
test/spec/Example.spec.js	Add a templating group using FeelTemplatingEntry in the demo setup.

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