[turinglambdaai]

Bug

Linux quick add clears the GTK entry before requesting parse_quick_add and add_task. If parsing or persistence fails, the user permanently loses their typed task. The code also allows repeated Enter/plus submissions while the first RPC is pending, producing duplicate tasks.

Fix

• Keep the submitted text in the entry until the backend reports a successful add. On parsing or saving errors, preserve the input and report the backend error.
• Guard concurrent submits with an in-flight flag, resetting it for success, errors and disconnected backend cases.
• Clear input and preview only if its current text still matches the submitted draft. A new task typed during an in-flight RPC is never erased by the older operation.
• Capture the selected or default target list ID before either asynchronous RPC so changing lists cannot redirect a task.
• Reject whitespace-only submissions without clearing user input; use the same quick-add grammar as Windows/macOS.

QA

• Linux GTK build + packaged acceptance green
• 生活 selected → Enter creates one task in 生活; quick repeated Enter doesn't duplicate it
• Backend parse/save failure keeps the exact text; retry works
• Start task A, edit to draft B before A finishes; A success doesn't remove B
• New task/preview still operate normally; undo-banner task restoration unaffected

Independent of #33 (Linux selection) and #34 (divider CSS); these branches touch different areas of the same file, so review the combined Linux build before release.