Renumbers the v2 migrations 044-052 to 045-053 behind main's
044_ClearAutomaticProjectModelDefaults, and adopts main's sticky
new-thread selection (#9164), local-only worktree bases in the v2 launch
path (#8751), the PR summary read for settlement (#9176), Claude per-cwd
skills (#9210), the provider editor redesign with the branch's dedicated
environment fields re-grafted (#8508), and the client half of
continue-threads-across-restart (#9167). The server-side continuation
markers stay unported: they live in the v1 session directory, and v2
recovery terminalizes running runs on restart, so the capability is
withheld until the v2 runtime carries them.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>