Collapse the four IBackgroundRequestOptions / ISubagentRequestOptions /
ISummarizationRequestOptions / IMainAgentRequestOptions interfaces into
a single 'as const' object + derived type, matching the existing
ToolName / ContributedToolName pattern in this codebase. Call sites now
use RequestKind.MainAgent etc. instead of hand-typing 'mainagent', so a
future rename only has to update the RequestKind definition.
Compile-time safety is unchanged — IRequestKindOptions.kind is still
typed as the union of literals.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Kevin KentandCopilot
26f1db756d