fix(core): match a Takeout sidecar by prefix only where Google cut its name

The prefix rule for sidecars whose names Google cut at 51 characters also
matched names that were never cut, so IMG_1.jpg's sidecar gave its title
and date to an IMG_12.jpg that had none. It now applies only to a sidecar
name at the cap. Edited copies, which have no sidecar of their own, take
their original's date by a rule of their own and keep their own name
(B225).

docs/BUGS.md

@@ -100,6 +100,7 @@ a live account since.
 
 | Entry | Title |
 |---|---|
+| [B225](#b225--a-takeout-photo-without-a-sidecar-takes-a-siblings-name-and-date) | A Takeout photo without a sidecar takes a sibling's name and date |
 | [B223](#b223--a-damaged-config-file-is-replaced-with-defaults-on-the-next-settings-change) | A damaged config file is replaced with defaults on the next settings change |
 | [B224](#b224--fallocate-zero-ranges-are-undone-and-collapse-ranges-corrupt-the-file) | `fallocate` zero ranges are undone and collapse ranges corrupt the file |
 | [B222](#b222--a-full-disk-at-close-is-reported-to-nobody-and-fsync-on-a-read-only-file-fails) | A full disk at close is reported to nobody, and `fsync` on a read-only file fails |
@@ -327,6 +328,35 @@ a live account since.
 
 Newest first.
 
+### B225 — A Takeout photo without a sidecar takes a sibling's name and date
+
+**Status:** Fixed, not verified live
+**Found:** 2026-10-16, architecture audit (`FINDINGS.md` 1.11). A scratch import through
+`scan_archives` gave `IMG_12.jpg`, which had no sidecar, the name `IMG_1.jpg` and IMG_1's capture
+time. It gave `IMG_2-edited.jpg` the title of its original.
+**Where:** `sidecar_rank`, `find_sidecar` and `is_edited_copy_of` in
+`crates/pdfs-core/src/takeout.rs`
+
+**Repro:** Import a Takeout folder holding `IMG_1.jpg` with its sidecar and `IMG_12.jpg` without
+one.
+
+**Cause.** The last matching rule accepted any sidecar whose stem, cut at a `.`, was a prefix of
+the photo's name. That rule exists for sidecar names Google cut at its 51-character cap, but it
+also matched short names that had not been cut, so `IMG_1`'s sidecar claimed `IMG_12.jpg`. The
+photo then went up under another photo's title and date, and two photos ended up with the same
+name. Edited copies, which Google exports without a sidecar of their own, matched the same way
+and took their original's title.
+
+**Fix.** The prefix rule applies only to a sidecar name that reaches the cap. An edited copy,
+`<original>-<word>.<ext>` with the word in any language, is matched to its original's sidecar
+by its own rule. It takes the capture time from that sidecar and keeps its own name.
+
+**Test:** `takeout::tests::a_photo_without_a_sidecar_does_not_take_a_shorter_named_siblings`,
+`takeout::tests::an_edited_copy_takes_its_originals_date_and_keeps_its_name`,
+`takeout::tests::longest_prefix_wins_when_the_photo_name_itself_was_truncated`.
+
+---
+
 ### B223 — A damaged config file is replaced with defaults on the next settings change
 
 **Status:** Fixed, not verified live