The events without a semantic builder (MT call, IMS registration, slices, ...)
are network-sourced, but the raw `envelope` action had no `src` override - the
only way to express them was the semantic set. `envelope` now accepts
`src` (82 terminal / 83 network) exactly like the `event` action; the step
editor exposes it and the authoring guide gets the row.
Also: the guide marks `por` as SCP80-only (the normaliser refuses it
elsewhere) and the semantic-events section names the shared src override.
Tests: 813 frontend + 717 Python; sw cache simple-v382.
catarrh
1aa1b44063