Merge origin/main into mackinnonbuck-sdk-github-telemetry-contract

Brings in the @github/copilot 1.0.66 bump (#1859), which re-ran the code
generators and added new RPC/session types (SessionLimits*, SessionCompletions,
AdaptiveThinkingSupport, etc.).

Conflicts were limited to generated files (dotnet Rpc.cs, python rpc.py).
Resolved by installing 1.0.66 and re-running `scripts/codegen` with the
telemetry schema overlay, so every generated file is a consistent product of
the 1.0.66 schema plus the experimental GitHub telemetry additions rather than
a hand-merged blend. Verified 1.0.66 still does not ship the telemetry types,
so the overlay remains required. Codegen is idempotent (re-running produces no
diff) and the hand-written telemetry glue (including the Node conditional-spread
opt-in) is unchanged.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: MackinnonBuck