fix: enable clipboard image export, release a paste when its window closes, and skip ordered-out windows in window_appears

[iamnbutler]

Fixes the #96, #99 and #89 failures from the full live check against the installed 0.13.1.

#96: save_path refused (CLIPBOARD_WRITE_FAILED / not supported). peekaboo-clipboard-image-export.patch added clipboardImageExport, but not to Peekaboo's remoteDefaultAllowlist. The embedded host intersects its allowed operations with the embedded allowlist built from that list, so it dropped the export. New patch peekaboo-clipboard-image-export-allowlist.patch adds it. src/build.ts now fails the build if any operation in runtime.swift's allowedOperations would be dropped. The export was the only one.

#99 and the stuck clipboard. The harness pasted an image into an .rtf TextEdit document. TextEdit opened its "Convert to RTFD?" sheet, the paste never landed, and the paste reservation then refused every clipboard write until TextEdit quits. That broke the harness's own clipboard writes and its restore. New patch peekaboo-paste-window-release.patch also releases the reservation when the receiver window is gone, or its number now belongs to another process. The harness now pastes into an .rtfd fixture.

#89.

• "Never holds" used desktop_key. Background keys come back completed, and expect leaves those alone, as documented. It now uses desktop_system_key f19.
• Spotlight: on macOS 27, Command-Space Spotlight is hosted by Siri AI (com.apple.campo). It keeps its panel listed while ordered out (off screen, on the current Space), and window_appears counted that as already open. window_appears now skips a window that is off screen on its display's current Space, unless its app is hidden. The harness picks whichever Spotlight host is running, and sends Escape only after Spotlight was seen open.

Verified

• npm test (75 pass) and npm run check.
• Native build with the new patches and the allowlist check.
• ClipboardPasteTransactionGateTests: 19 pass, including the new window-release test.
• PeekabooEmbeddedBridgeRuntimeTests: 12 pass, including the export allowlist assertion.
• Live, installed host, --only 89: 3/3 pass.
• Not yet live-verified: feat: save the clipboard image's original bytes with desktop_clipboard_read save_path #96 and feat: paste an image or files into a native text area with desktop_insert, or leave the clipboard replaced on request #99 need a host with these patches (dev app or release).