fix(editor): Fix '=' handling in expressions

[elsmr]

Summary

• Typing = in a fixed input should switch to expressions
• Fix: Typing = in a expression input should insert a = (should not disappear in any case)
• New: Typing Backspace in an empty expression input switches back to fixed
• Fix: auto bracket closing should overwrite manually typed closing brackets (instead of duplicating)
• Cleanup unused code

Screen.Recording.2025-02-07.at.15.27.45.mov

Related Linear tickets, Github issues, and Community forum posts

https://linear.app/n8n/issue/NODE-2176/community-issue-google-sheet-node-removes-the-=-for-formulas
fixes #12194

Review / Merge checklist

• PR title and summary are descriptive. (conventions)
• Docs updated or follow-up ticket created.
• Tests included.
• PR Labeled with release/backport (if the PR is an urgent fix that needs to be backported)

[codecov]

Codecov Report

Attention: Patch coverage is 71.42857% with 20 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../src/plugins/codemirror/expressionCloseBrackets.ts	67.85%	9 Missing ⚠️
...tor-ui/src/plugins/codemirror/completions/utils.ts	41.66%	7 Missing ⚠️
...neExpressionEditor/InlineExpressionEditorInput.vue	81.81%	2 Missing ⚠️
...ckages/editor-ui/src/components/ParameterInput.vue	0.00%	2 Missing ⚠️

📢 Thoughts on this report? Let us know!

[ShireenMissi]

I tested manually and it all works as expected except for closing brackets see the screen recording

Screen.Recording.2025-02-07.at.17.03.11.mov