v1.0.40: fix duplicate timer race condition on rapid double-press

onKeyDown is async and calls await startTimer (~1s network). A second
press before that resolves saw the same state (isRunning=false,
memRunningEntryId=null) and created a second Notion entry. Only the
last startTimer call's ID was tracked, orphaning the first entry
running indefinitely in Notion.

pendingKeyDown Set acts as a per-action mutex: a second press while the
first is in-flight is dropped. try/finally guarantees the lock is always
released.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

com.pdma.notion-timer.sdPlugin/bin/plugin.js.sig

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