fix: allow tabbing out of CodeMirror editors

[jarekdanielak]

Related to https://github.com/camunda/camunda-hub/pull/21494#pullrequestreview-3966387333

Proposed Changes

Allow tabbing out of CodeMirror editors in the variable value box.

In the screencasts I'm spamming TAB.

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[jarekdanielak]

@yT0n1 just FYI, I haven't forgotten about the bug you reported in the review. 😉

[Copilot]

Pull request overview

This PR updates the CodeMirror JSON “interactive controls” tab-navigation so users can tab out of the read-only value editor, instead of being trapped in a wrap-around focus loop. This improves keyboard accessibility and usability in the variable value box.

Changes:

• Update moveFocus() to stop wrapping focus when tabbing past the first/last interactive token.
• Clear the active token and return false at bounds so the browser can handle Tab/Shift+Tab and move focus out of the editor.

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[Copilot]

This changes the Tab/Shift+Tab focus behavior (no wrap-around, allow leaving the editor) but there’s no automated test covering it. Since CodeMirror behavior can regress easily with extension/keymap changes, please add a browser test (e.g., in lib/components/VariableRow/test/ValueDisplay.spec.jsx) that focuses the editor, presses Tab until the last interactive token, and verifies focus moves to the next focusable element (and similarly Shift+Tab moves to the previous element when tabbing past the first token).