Prevent 't' toolbox shortcut from inserting into toolbox search

[tracygardner]

Motivation

• Pressing the t shortcut to open the toolbox also inserted the letter into the toolbox search input and could trigger synchronous indexing, causing a noticeable delay.

Description

• Add a capture-phase keydown listener inside createBlocklyWorkspace that prevents the default action for an unmodified t keypress when the active element is not a text input or contentEditable, stopping the character from reaching the toolbox search field.
• The handler explicitly ignores events with Ctrl/Meta/Alt modifiers and does not change typing behavior when focus is inside inputs or editable regions.

Testing

• No automated tests were run for this change.

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Codex Task