Both message parsers accepted untyped input and relied on scattered
asRecord/asString calls to extract fields at runtime. With the
discriminated ChatMessagePart union, both accept typed input directly
and narrow via switch (part.type).
parseMessageContent narrows from (content: unknown) to
(content: readonly ChatMessagePart[] | undefined), removing legacy
input shape handling the Go backend normalizes away.
applyMessagePartToStreamState narrows from Record<string, unknown>
to ChatMessagePart.
The SSE type guards had a & Record<string, unknown> intersection
that widened everything untyped downstream. Since the data comes
from our own API, the intersection was removed and all handlers in
ChatContext now use generated types directly.
Fixes tool_call_id and tool_name variant tags in codersdk/chats.go:
marked optional to match reality (Go guards against empty values,
omitempty omits them at the wire level).
Refs #23168, #23175
Mathias Fredriksson
8b4d35798a