fix: handle recording discard and write-failure in cursor telemetry buffer

Address two issues raised during review:

P1 – When a recording is cancelled or restarted, setRecordingState(false)
enqueues its cursor batch but store-recorded-session is never called,
leaving a stale batch that contaminates the next recording's telemetry.
Add discardLatestPending() to the buffer and a discard-cursor-telemetry
IPC handler; the renderer now calls it on the discard path.

P2 – takeNextBatch() dequeued the batch before fs.writeFile, so a write
failure would permanently lose the telemetry. Wrap the write in
try/catch and re-insert the batch via prependBatch() on failure.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/hooks/useScreenRecorder.ts

@@ -225,6 +225,7 @@ export function useScreenRecorder(): UseScreenRecorderReturn {
 				try {
 					const screenBlob = await activeScreenRecorder.recordedBlobPromise;
 					if (discardRecordingId.current === activeRecordingId) {
+						window.electronAPI?.discardCursorTelemetry();
 						return;
 					}
 					if (screenBlob.size === 0) {