(restore): quit during a restore can save a duplicate fresh session or drop an attaching continuation #550

Follow-ups from the review of #548 (integration of #477, #479 and #518). Neither PR shows these alone: the scheduled saves stop during runRestore, and only #479's final exit flush reaches the windows below.

1. A quit during a fresh restore saves two new sessions. launchNewSession (public/app.js:1349,1363) adds the new id to pendingSessions/openSessions before await openTerminal, while the fresh item is still in restoreInFlight. A quit in that window saves [{cleared, active, fresh}, {started-1, fresh}], and the next start opens two new sessions in the project. Repro written outside the repo. Fix: drop the in-flight fresh item once this restore has created a pending session for its project.
2. A quit while a continuation opens as attach drops it from the saved set. The entry is open with attach=true and item.sessionId is already the new id (app.js:310), but keepAttached is set only after the open returns (:329, :1550). The held filter (app.js:210) skips it. Fix: also keep entries that are open as attach and still in restoreInFlight.
3. clearOwner on the process-table path is untested. test/cli-session-state.test.js:540-561 injects readParentPid, which turns the table off. Add a test with readProcessTable injected and win32 as the platform.

All three are narrow: a quit during restore, and a test gap. Bugs 1 and 2 are red-first.