Add support for local variables for loop events (While, For Each...) and loop index variable

[4ian]

• Add support for local variables to all these events
• Add support for local variables for all variables of "For Each Child Variable"
• Add support for adding a "loop counter" variable. This is actually a local variable.

Some examples:

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[4ian]

@codex review

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Make loop index edits honor dialog cancel

The onRenameIndexVariable handler mutates editedVariableLoopEvent immediately while the local-variables dialog is open, but LocalVariablesDialog cancel restoration only serializes/unserializes the variables container. If the user renames/removes the loop counter and presses Cancel, the variable data is reverted but indexVariableName stays modified, leaving the loop event referencing the wrong variable (or no local variable at all) and changing runtime behavior unexpectedly.

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