Paint applied highlights natively (yellow) and immediately; suppress echo color

Two rendering observations from live use:

- Synced highlights rendered grey while device-native ones are yellow:
  KOReader natively stamps view.highlight.saved_color ("yellow" on
  color screens) onto every new highlight; a nil color takes the
  darkenRect path (grey). Applied entries now carry the device's own
  saved_color, so they look exactly like native ones.

- They only appeared after a restart: ReaderView caches each rendered
  page's highlight boxes and only invalidates the cache on
  AnnotationsModified — a plain setDirty repaints from the stale
  cache. applyServerAnnotations now dispatches AnnotationsModified
  with a non-table payload (clears the whole cache) before setDirty.

Echo safety for the new default color: an applied entry's yellow is
the device default, not user intent — pushing it back would clobber
the web color. collectAnnotations suppresses the color for entries we
applied (bookhoard_dedup_key set) that the user has not modified
since (datetime_updated, which KOReader sets on any edit); edited
entries push their color and the server lets the edit win. Verified
in the harness: applied entry gets color=yellow; un-edited echo
carries no color; an edited (datetime_updated + green) echo sends
green and the web row updates; dedup keys round-trip throughout.

main.lua

@@ -876,6 +876,20 @@ function Bookhoard:collectAnnotations()
         return p or ""
     end
 
+    local function echoColor(bm)
+        -- Color the device can vouch for as user intent:
+        --  - entries we applied ourselves carry the device DEFAULT color
+        --    (set at apply time); pushing it back would clobber the web
+        --    color. Suppress it unless the user has edited the entry since
+        --    (datetime_updated — set by KOReader on any modification).
+        --  - device-native entries carry a user-chosen (or default) color;
+        --    those push their color as before.
+        if bm.bookhoard_dedup_key and not bm.datetime_updated then
+            return nil
+        end
+        return bm.color
+    end
+
     for _, bm in ipairs(entries) do
         local sel_text, user_note
         if model == "v2" then
@@ -936,8 +950,9 @@ function Bookhoard:collectAnnotations()
             table.insert(notes, entry)
         elseif has_text then
             entry.type = "highlight"
-            if bm.color then
-                entry.color = bm.color
+            local ec = echoColor(bm)
+            if ec then
+                entry.color = ec
             end
             table.insert(highlights, entry)
         else
@@ -1325,10 +1340,15 @@ function Bookhoard:applyServerAnnotations(annotations)
                 entry.drawer = "lighten"
                 entry.text = srv_text
                 if srv_notes ~= "" then entry.note = srv_notes end
-                -- No color imposed: devices render their own default and
-                -- cannot round-trip web colors; the web color only changes
-                -- when the highlight is edited here (the edit sets a device
-                -- color, which syncs back by name).
+                -- Match the device's native highlight look exactly: native
+                -- highlights carry view.highlight.saved_color ("yellow" on
+                -- color screens); a nil color renders grey (darkenRect).
+                -- Synced entries still never push this color back (see
+                -- collectAnnotations) — the web color only changes when the
+                -- highlight is edited here.
+                local default_color = (self.ui.view and self.ui.view.highlight
+                    and self.ui.view.highlight.saved_color) or "yellow"
+                entry.color = default_color
             else
                 if srv_text ~= "" then entry.note = srv_text end -- bookmark label
             end
@@ -1426,8 +1446,12 @@ function Bookhoard:applyServerAnnotations(annotations)
         if self.ui.saveSettings then
             self.ui:saveSettings()
         end
-        -- ReaderView paints annotations from the model on each repaint;
-        -- request one so applied highlights appear immediately.
+        -- ReaderView caches each rendered page's highlight boxes and only
+        -- invalidates them on AnnotationsModified — without this, applied
+        -- annotations don't paint until restart despite the repaint.
+        -- A non-table payload clears the whole cache (per-item payloads
+        -- only remove the pages of the listed items).
+        self.ui:handleEvent(Event:new("AnnotationsModified", nil))
         if self.ui.dialog then
             UIManager:setDirty(self.ui.dialog, "ui")
         end