Address review notes on #2248:
- readTextFromClipboard's WSL branch now mirrors readImageViaPowerShell
(Bun.spawn + kill timer sharing POWERSHELL_TIMEOUT_MS) instead of
execSync, so a cold powershell.exe start cannot block the TUI event
loop on the first smart-paste miss.
- The smart-paste text fallback routes through ui.getFocused() +
hasPasteText like the enhanced-paste text path, so the payload lands
in focused modal Input prompts instead of the hidden main editor
(#2127 contract). Covered by a new routing test.
app.clipboard.pasteImage dead-ended with a status message when the
clipboard held text, which made the chord useless on hosts that only
deliver that one keypress (VS Code's integrated terminal forwarding
Ctrl+V, Windows clipboard history via Win+V simulating Ctrl+V).
- handleImagePaste now pastes clipboard text through the editor's
paste semantics when no image is available; an empty clipboard
reports 'Clipboard is empty'.
- readTextFromClipboard reaches the Windows clipboard through host
PowerShell under WSL (mirroring readImageFromClipboard), with CRLF
normalization and UTF-8 output encoding.
- handleClipboardTextRawPaste's empty-clipboard status message moved
to the actual empty branch (was shown after successful pastes).
- Clipboard reads are constructor-injectable for tests.
Implements proposal 1 of #1628.