[Blueprint Editor] Add multiline string editor modal (#2962)

Editing PHP code or SQL queries inside Blueprint JSON is painful because
newlines become `\n` escape sequences. This adds a modal editor that
lets you edit string values as actual multiline text with proper syntax
highlighting.

When your cursor is inside a string value, a floating "Multiline Edit"
toolbar appears above it. You can also press Cmd/Ctrl+E. The modal opens
with the string content unescaped and syntax-highlighted based on the
step type—PHP for `runPHP` steps, SQL for `runSQL`, and so on. If the
step type doesn't give enough context, it falls back to detecting the
language from the content itself (looking for `<?php`, SQL keywords,
HTML tags, or Markdown patterns). You can always override the detected
language with the dropdown.


https://github.com/user-attachments/assets/68231869-2f4b-4ac2-95f4-96711f73abc1

When you save, the content is escaped back to valid JSON and inserted
into the document.

Author: adamziel

package-lock.json

@@ -74,6 +74,7 @@
 		"@codemirror/lang-javascript": "6.2.4",
 		"@codemirror/lang-json": "6.0.2",
 		"@codemirror/lang-markdown": "6.3.4",
+		"@codemirror/lang-sql": "6.8.0",
 		"@codemirror/lang-php": "6.0.2",
 		"@codemirror/language": "6.11.3",
 		"@codemirror/search": "6.5.11",