* feat(gateway): carry machine class through session moves
Profile move targets accept an optional machineClass with new-session
parity: validated in the protocol, persisted on the durable move intent
(bare nullable column, lazy same-version ALTER), replayed exactly by
restart recovery, and selectable from the Control UI move dialog.
Moving to the current profile with a different class resizes the
session's worker.
* fix(gateway): project placement facts on chat startup
chat.startup and chat.history built sessionInfo without the placement
projection sessions.list applies, so clients merging that row erased a
live worker placement and its move intent — the Runs on Cloud chip
disappeared after any turn until a full reload.
Reuse the canonical ensureColumn helper for the move table's additive
column instead of a hand-rolled PRAGMA read.
Peter Steinberger
57e862980b
