Add sfdupes info: show the database's details (closes #117)

info prints the database's path and source, the sizes of the database
file and its -wal file, when the database file last changed, the schema
version and the record counts, one per line as a name, a tab and the
value. It opens the database as report does and shows an open and a
count phase on stderr. The schema version and the counts come from one
read-only transaction, the counts from one query.

seedDatabase now closes test databases out of WAL mode, as scan does;
otherwise info's own connection creates an empty -wal file. The open
phase's name and text became constants for the linter, and the scan
command moved to newScanCommand to keep newRootCommand short enough.

Judgement call: the lines are written after the last display ends, so they skip the display's stdout writer.

Model: opus-5-5

TODO.md

@@ -29,6 +29,16 @@
 
 # Completed Steps
 
+- new subcommand `info` prints the database's details on stdout, one per line as
+  a name, a tab and the value: its path and where it came from, the sizes of the
+  database file and of its `-wal` file when there is one, when the database file
+  was last changed, the schema version, the number of records, how many have
+  head and tail hashes and how many a content hash, and the sizes of all records
+  added up. It opens the database as `report` does, and shows two phases on
+  stderr, `[1/2] open` and `[2/2] count`; the schema version and the counts come
+  from one read-only transaction, the counts from one query (2026-10-16,
+  https://git.eeqj.de/sneak/sfdupes/issues/117)
+
 - `report` shows its work on stderr in two phases, `[1/2] open` and
   `[2/2] read`, with the progress display `scan` and `trees` use, from the
   moment it starts until the summary line: `open` says it is opening the