Format the rewritten documents with prettier

Re-wraps README.md, docs/ARCHITECTURE.md, docs/DATAMODEL.md,
docs/REPOSTRUCTURE.md and the roadmap in docs/TODO.md with `make fmt`,
which now runs prettier on Markdown. Only line wrapping changes; the
words are those that passed review at 4da102c.

Model: fable-5-1

docs/DATAMODEL.md

@@ -76,8 +76,8 @@ One row for each backed-up path: a regular file, a symlink or a directory.
 
 - `id`: a UUID. Primary key.
 - `path`: the absolute path. Unique.
-- `source_path`: the configured path under which the scan found this entry,
-  made absolute with symlinks resolved. A restore does not read it.
+- `source_path`: the configured path under which the scan found this entry, made
+  absolute with symlinks resolved. A restore does not read it.
 - `mtime`: the modification time.
 - `mtime_nsec`: the nanoseconds within that second.
 - `size`: the size in bytes.
@@ -88,9 +88,9 @@ One row for each backed-up path: a regular file, a symlink or a directory.
 
 `idx_files_path` indexes `path`.
 
-There is one row for each path, and it is updated when the file changes. The
-row is shared by every snapshot in the local index that lists the path. An
-older snapshot's own view of the file is in that snapshot's database at the
+There is one row for each path, and it is updated when the file changes. The row
+is shared by every snapshot in the local index that lists the path. An older
+snapshot's own view of the file is in that snapshot's database at the
 destination.
 
 ### `chunks`
@@ -176,8 +176,8 @@ One row for each snapshot.
 - `new_chunk_size`: the total size of those chunks before compression.
 - `blob_count`: the number of blobs this snapshot created.
 - `total_size`: the total size of all files in the snapshot.
-- `uncompressed_chunk_size`: the total size, before compression, of the
-  distinct chunks the snapshot's files use.
+- `uncompressed_chunk_size`: the total size, before compression, of the distinct
+  chunks the snapshot's files use.
 - `blob_size`: the total compressed size of the blobs the snapshot uses.
 - `blob_uncompressed_size`: the total uncompressed size of those blobs.
 - `compression_ratio`: the compression ratio of those blobs.
@@ -192,11 +192,11 @@ example is `server1_home_2025-06-01T12:00:00Z`. It has three parts:
 - the snapshot name
 - the start time, in UTC
 
-The `snapshot list` table shows `uncompressed_chunk_size` as
-`UNCOMPRESSED SIZE` and `new_chunk_size` as `NEW CHUNK SIZE`.
+The `snapshot list` table shows `uncompressed_chunk_size` as `UNCOMPRESSED SIZE`
+and `new_chunk_size` as `NEW CHUNK SIZE`.
 
-A snapshot with `completed_at` set to `NULL` is unfinished. `snapshot list`
-does not show it. The next backup deletes it, and so does `prune`.
+A snapshot with `completed_at` set to `NULL` is unfinished. `snapshot list` does
+not show it. The next backup deletes it, and so does `prune`.
 
 ### `snapshot_files`
 
@@ -268,8 +268,8 @@ Settings that belong to this copy of the index.
 - `key`: the name of the setting. Primary key.
 - `value`: its value.
 
-The only key is `storage_url`. It holds the destination that the index was
-first used with. These commands refuse to run when the config names a different
+The only key is `storage_url`. It holds the destination that the index was first
+used with. These commands refuse to run when the config names a different
 destination:
 
 - `snapshot create`
@@ -361,8 +361,8 @@ still be in the `-wal` file beside it.
 
 ### Restore
 
-A restore reads no file, chunk or blob rows from the local index. Given a
-remote key, it reads `snapshots` and `local_meta` there to check the destination
+A restore reads no file, chunk or blob rows from the local index. Given a remote
+key, it reads `snapshots` and `local_meta` there to check the destination
 marker.
 
 - It downloads and decrypts `db.zst.age` into a temporary directory.