Carry file size, thumbnail size, and deletion flag through decryptFile (closes #37)

Foundation unit for the cache/API design. Three fields arrived on the wire
but decryptFile dropped them:

- `file.size` from `info.fileSize` and `thumbnail.size` from `info.thumbSize`,
  left `undefined` when the server omits `info`.
- `isDeleted` carried from the diff row onto `EnteFile`.

No caller change: `listFiles` still filters deleted rows before decrypt, so no
deleted row reaches decryptFile here. Surfacing a deleted file through
decryption belongs to the enumeration unit, issue 38, where the return shape
can be designed around where such a row actually flows.

Model: opus-4-8

TODO.md

@@ -18,6 +18,13 @@ Update the README API reference section to match the current implementation.
 
 # Completed Steps
 
+- 2026-09-22: Carried file size, thumbnail size, and the deletion flag through
+  `decryptFile` (issue 37, foundation for the cache/API design). Live files now
+  populate `file.size`/`thumbnail.size` from the server's `info` (left
+  `undefined` when the server omits it), and `isDeleted` is carried from the
+  diff row onto `EnteFile`. No caller change: `listFiles` still filters deleted
+  rows before decrypting. Surfacing a tombstone through decryption belongs to
+  the enumeration unit (issue 38).
 - 2026-08-10: Made `lint-once.test.ts` enforce what its header claims. It walked
   `make check` only, so it never read `Dockerfile` — the image CI builds through
   `script/cibuild` — and a second `prettier --check .` could be added there with