[FEATURE]: Auto-enter edit mode when typing on 'Type your own answer' in question prompt #34476

Feature hasn't been suggested before.

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Describe the enhancement you want to request

When the agent asks a question via the Question tool and the user navigates to the "Type your own answer" option, they must press Enter to enter edit mode before they can start typing. This is an unnecessary keystroke — if you've already selected the custom answer option, the intent to type is clear.

Proposed change: When "Type your own answer" is the selected (highlighted) option and the user presses any printable character, immediately enter edit mode and insert that character into the textarea. This removes the extra Enter keypress.

Navigation keys (↑↓/jk, h/l for tabs, Enter to confirm, Esc to dismiss) continue to work as before. Only printable characters trigger the auto-edit behavior.

Related issues: #30028 (inline input field proposal), #30393 (Enter swallowed in custom answer submission).