A fresh session's daemon creates an about:blank scratch tab on connect; a
subsequent `tab new <url>` then opened the work tab beside it, so every session's
tab group showed a stray 'about:blank' next to the real page (e.g. about:blank +
ChatGPT). tab_new now closes any OWNED, still-blank tab once a real (non-blank)
tab exists, and re-pins the new tab. Verified live: `tab new <url>` on a fresh
session leaves only the work tab. 870 tests pass.
leeguooooo
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