Slack inspector creates context with key: slack_channel
SlackQueryProcessor uses context to fetch users from that channel, returning User items (if found) or ephemeral Contact items with foreign keys.
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browser action button to toggle the sidebar. It communicates with context script by finding the active window/tab and then calling chrome.tabs.executeScript() to inject a small script which in turn does window.postMessage.
https://developer.chrome.com/extensions/tabs#method-executeScript
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