feat: name the save folder and the pack on screen

The plan and the result now say how many files go to the save folder and
where, from a new saves event. With --from-pack they say the files come
from the pack, not a download. A stop asked for (Start+Select, SIGHUP)
ends on the plain outcome, without the log's last lines.

wiki/installer.md

@@ -1304,6 +1304,7 @@ other schemas under `api/v1/schemas/`.
 | `declared` | `platform`, `files`, `present`, `missing`, `wrong_hash`, `bytes_needed`, `dests` | Right after `check`, the same counts over the files the platform's own list names (`cores: null`), and their `dests` in the order of the `file` events. A setup that checks its own list reads its answer here, with or without `--declared-only` |
 | `found` | `platform`, `dest`, `folder`, `path`, `member`, `reason` | Each file to install that this machine already holds, after `check` and before anything is written, in `--check` and `--dry-run` too. `folder` is the `--from` folder as given, or the `bios_dir` of the check when the BIOS folder holds the file at another place, and then `reason` says where in words (`nested folder: ...` for a misplaced file, `the same file is at ...` for one the list installs there too). `path` is the file, and `member` the ZIP member holding the bytes when `path` is an archive, an empty string otherwise. Its copy is reported by a `downloaded` event |
 | `unreadable` | `platform`, `folder`, `path`, `member`, `reason` | Each file in a `--from` folder that could not be read and may be one the run still needs, right after the `found` events: its size is that of a file no copy was found for, or unknown (a folder that could not be listed, a ZIP that would not open). `member` names the ZIP member, or is empty. `reason` says why in words (`Permission denied`, `it is encrypted, a password is needed`) |
+| `saves` | `platform`, `files`, `folder` | After `detect` and before `checking`, when the list holds files read from the frontend's save directory and that directory is known: how many, and the `folder` they go to, where `<system>` and `<core>` stand for one folder per system or per core. When it is not known, the files are counted in the summary's `skipped` instead (`no_save_directory`) |
 | `download` | `platform`, `files`, `bytes` | Before the downloads start. Counts the files copied from this machine too |
 | `progress` | `files_done`, `files_total`, `bytes_done`, `bytes_total` | At most every half second while bytes arrive |
 | `transfer` | `bytes_local`, `bytes_network` | Right after each `progress` event, and once when the files of a `download` event are done. It splits `bytes_done`: `bytes_local` came from this machine (a copy found by `--from` or in the BIOS folder, the pack, a partial copy resumed), `bytes_network` from the network. A download speed is `bytes_network` over the time elapsed |