why

• before this, if a stagehand instance was closed, then recreated, and a CDP url was provided in localBrowser.connect(), the provided CDP url would not get used: the extension would keep using the old one

what changed

• the extension now stores the CDP URL associated with the extension’s browser connection
• the extension will replace the connection when initialization supplies a different URL
• it will reuse reuse a connection when the URL matches or is omitted

test plan

• added a test that initializes with URL A, closes the Stagehand instance, then initializes with URL B and verifies the old connection closes before the new one opens.
• added a test that omits the URL on reinitialization and verifies the existing connection is reused.
• added a test that makes connection replacement fail, verifies the runtime stays idle with no connection, then retries successfully.
• updated the active-instance test to supply a different URL and verify reinitialization is still rejected

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Summary by cubic

Fixes the extension keeping a stale browser connection when a Stagehand instance is closed and recreated with a different CDP URL in localBrowser.connect().

• The runtime now stores the CDP URL for the active browser connection and, on re-initialization, replaces the connection when the URL differs and reuses it when the URL matches or is omitted.
• When replacement fails, the runtime stays idle so re-initialization can be retried.
• Adds a changeset and updates the bundled extension assets.