Review follow-up on #15380.
The RPC accepted `cursor` and `screen` together. The CLI refuses the pair, but
terminal.read is reachable without it, and honoring both answered with rendered
lines carrying the stream's pagination metadata — two frames of reference in one
payload, which is the confusion `source` exists to remove. The guard beside it,
withVisibleSnapshotFallback, already declines to substitute rendered lines when
a cursor is present; the screen path now agrees, at the RPC boundary where every
remote caller passes. Nothing could previously send both, since `screen` did not
exist, so rejecting breaks no existing caller.
The command notes and the runtime comment both still described the fallback as
`source: stream`, left over from renaming that value to `screen-unavailable`
during implementation. The spec text is surfaced through `orca help` and the
agent-context schema, so a caller following it would test for a value the code
never emits. Both now describe all four states, including that an absent source
means the host predates the field.
Neil
ef096d539d