Draft persistence: unsubmitted prompts are lost on focus change #1087

Feature Description

Typing a long, situation-based prompt (40+ lines) in the composer is easy to
lose: an accidental click/refocus wiped the entire input with no way back.

Unsubmitted composer text lives only in memory. Confirmed there is no draft
file in ~/.commandcode and ~/.commandcode/history.jsonl only gains an entry on
submit, so there is nothing to recover from.

Request: persist the composer draft (e.g. debounced autosave to a per-session
draft file), and restore it when the input is re-focused or the session is
resumed. Even a "restore last discarded input" binding would be enough.

Workaround I'm using now: Ctrl+G to compose in $EDITOR.

Use Case

No response

Additional Context

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