GitHub #2121/#2307: Windows browser clients intentionally skip first-tab
auto-create, but TerminalModal showed an endless 'Starting terminal...'
spinner whose only escape was the tab-strip '+'. useTerminalSessions now
exposes autoCreateDisabled and the modal renders an explicit 'Start
terminal' action instead. All-inactive persisted tab payloads are also
normalized on restore so the spinner can't wedge on activeTab=null.
Paste: attachCustomKeyEventHandler returning false does not cancel the
browser's default paste, so Ctrl/Cmd+V delivered the payload twice (custom
clipboard read + xterm helper-textarea paste event). preventDefault() makes
the custom read the single path; when the async clipboard API is missing
(non-HTTPS remote access, older Firefox) the handler returns true so the
native paste path works instead of paste being dead.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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