Echo duplication: devices push their full annotation list on every
sync, and an echo of a web-created annotation computed a different
dedup key than the original (device locators differ from web locators)
— every pull→push cycle minted a duplicate row, and cleaning those up
on the web tombstoned them back to the device, deleting the
just-applied copies. That was the "web highlights never appear on
KOReader" experience. GetMetadata now serves each annotation's
dedup_key; the device stores it on the applied entry and echoes it in
pushes; SaveHighlight/SaveBookmark/SaveNote accept a DedupKey
override so echoes converge onto the original row (verified: pull →
echo push creates no rows, LWW skips identical content).
Color semantics (per user preference): devices render their own
default and cannot round-trip web colors, so GetMetadata no longer
serves colors at all — every highlight syncs regardless of its web
color and the device draws its default. An echo carries no color;
ingest then PRESERVES the stored web color (existingHighlightColor
lookup by dedup key) so round-trips never change it. A non-empty
device color means the user edited the highlight there: it maps
name→hex (green→#a5d6a7, default yellow) and wins. Verified: echo
kept #ffd54f; a simulated device edit with "green" updated the web
row to #a5d6a7.
Classification: KOReader auto-fills text="in Chapter X" on page
bookmarks (ReaderAnnotation:updateItemByXPointer), so the plugin's
text-presence classification turned every echoed bookmark into a junk
highlight on the web. v2 classification now keys off the drawer field
(present = highlight/note, absent = bookmark with its label in note).