Adopts the round's main features into the v2 architecture: the #9023
media rework (streamed videos, media-file assets, protocol-relative
links), #9098 shared live-activity row folded into the v2 working and
thinking rows, the #9084/#9078 Claude model catalog for v2 consumers,
a native #9005 OpenCode child-session abort in the v2 adapter, #9013's
landed LegendList patch, and per-environment sidebar provider entries.
For #8600 the server-side pieces land, but auto-settle evaluation stays
client-side (reading the new server-owned settings) until the v2
orchestrator grows its own settlement reactor; main's v1-only reactor
and coalescer additions are dropped with the rest of the v1 path.

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