An ID on the command line is decimal digits only (closes #185)

files --collection, get, get-thumb and helper fix-missing-thumbnails
--file read an ID with Number(), so 0x10 meant 16, 1e3 meant 1000 and
an empty string meant 0, and --file dropped an ID it could not read.
parseID in src/cli-commands.ts now takes an ID only when it is decimal
digits and a safe integer; anything else prints "Invalid file ID: ARG"
or "Invalid collection ID: ARG" and the command exits 1. The fixer
checks every --file ID before it opens the library, so one bad ID fails
the whole command before any request.

Model: opus-5-5

TODO.md

@@ -25,6 +25,15 @@ declares one.
 
 # Completed Steps
 
+- 2026-10-14: `files --collection`, `get`, `get-thumb` and
+  `helper fix-missing-thumbnails --file` take an ID only when it is written in
+  decimal digits and is a safe integer (issue 185). Before, `Number()` read
+  `0x10` as 16, `1e3` as 1000 and an empty string as 0, and `--file` dropped an
+  ID it could not read without a word. Anything else now prints
+  `Invalid file ID: <arg>` or `Invalid collection ID: <arg>` and exits 1 before
+  any request; one bad `--file` ID fails the whole command. `parseID` in
+  `src/cli-commands.ts` does the check for all four.
+
 - 2026-10-06: The README says how to run `quak backup` from cron (issue 170):
   log in once as the job's user, a crontab with a backup every night and
   `--verify` on Sundays appending to a log file, and the `HOME` and