fix: rescue orphaned annotations to root in the pane

Found by loading the real Challengers project through re-frame-test:
3 of 15 stored annotations were filed under a since-deleted parent.
Under the :in model their sole host was a ghost, so ::all-annotations
never surfaced them — invisible and unrefileable.

::all-annotations now drops :in hosts that no longer exist and rescues an
annotation left with none to root (full-scene context, so peer-delta safe).

Tests (re-frame-test, high-level events + pane sub):
- orphaned-annotation-is-rescued-to-root
- legacy-parent-data-migrates-through-peer-delta (the real DB shape)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tl/src/tl/subs.cljs

@@ -135,11 +135,16 @@
  :<- [::scene] :<- [::context] :<- [::segments] :<- [::revealed]
  (fn [[scene ctx segs revealed] _]
    (let [ann?    (fn [gid] (= :annotation (:type (get-in scene [:groups gid]))))
+         exists? (fn [x] (contains? (:groups scene) x))
          ;; each annotation → the mark-groups it's FILED UNDER (:in membership). A
          ;; normal annotation has one; a linked one has several, so it lists under
-         ;; each. Asserted, not derived from where marks resolve.
+         ;; each. Asserted, not derived from where marks resolve. Any :in host that
+         ;; no longer exists (its group was deleted) is dropped; an annotation left
+         ;; with NO surviving host is rescued to root so it stays visible/refileable
+         ;; instead of vanishing into a ghost parent.
          parents (into {} (for [[gid g] (:groups scene) :when (= :annotation (:type g))]
-                            [gid (scene/membership scene gid)]))
+                            (let [ms (filter exists? (scene/membership scene gid))]
+                              [gid (if (seq ms) (set ms) #{:root})])))
          ;; child count per timeline (drives the "Show N" nested badge)
          nested  (reduce (fn [acc ps] (reduce #(update %1 %2 (fnil inc 0)) acc ps)) {} (vals parents))
          ;; membership-reveal hierarchy: shows when ctx is a host it's filed under,

tl/test/tl/flow_test.cljs

@@ -190,10 +190,48 @@
      (rf/dispatch [::ev/toggle-children :annA])
      (is (contains? (pane-ids) :annC) "revealed → annC shows as annA's child at root"))))
 
+;; =========================================================================
+;; real-data hazard: an annotation whose only host was deleted (an orphan)
+;; must NOT vanish — the pane rescues it to root so it stays refileable.
+;; (found by loading the actual Challengers project: 3/15 annotations were
+;; filed under a since-deleted parent.)
+;; =========================================================================
+
+(deftest orphaned-annotation-is-rescued-to-root
+  (rf-test/run-test-sync
+   ;; annC's sole host (annA) is deleted out from under it, as if by restore of
+   ;; stale data or a peer deleting the parent
+   (setup! (update (seed) :groups dissoc :annA) [:root])
+   (testing "annC's :in still points at the now-missing annA"
+     (is (= [:annA] (:in (get-in (scene*) [:groups :annC]))))
+     (is (nil? (get-in (scene*) [:groups :annA]))))
+   (testing "but the pane rescues it to root rather than dropping it"
+     (is (contains? (pane-ids) :annC) "orphan is visible at root, not lost")
+     (is (= #{:root} (:parents (card :annC))) "listed under root until re-filed"))
+   (testing "and it can be re-filed normally from there"
+     (rf/dispatch [::ev/file-into :annC :annB])
+     (is (contains? (s/membership (scene*) :annC) :annB)))))
+
 ;; =========================================================================
 ;; JSON wire round-trip of :in (vector, keyworded) via restore-annotations
 ;; =========================================================================
 
+(deftest legacy-parent-data-migrates-through-peer-delta
+  (rf-test/run-test-sync
+   (setup! clips-scene [:root])
+   ;; a reload/peer delivers a legacy annotation — string :parent, no :in, exactly
+   ;; the shape stored in the real DB before the membership migration
+   (rf/dispatch [::ev/peer-delta
+                 {:changed {:ann-legacy {:type "annotation" :parent "root" :name "L"
+                                         :marks [{:id "lm" :start {:ref "clip-a" :at 0}
+                                                          :end {:ref "clip-a" :at 50}}]}}
+                  :deleted []}])
+   (testing "it migrates :parent -> :in [:root] on ingest and drops the old field"
+     (is (= [:root] (:in (get-in (scene*) [:groups :ann-legacy]))))
+     (is (nil? (:parent (get-in (scene*) [:groups :ann-legacy])))))
+   (testing "and shows up in the root pane like any other"
+     (is (contains? (pane-ids) :ann-legacy)))))
+
 (deftest membership-survives-the-json-wire
   (rf-test/run-test-sync
    (setup! (seed) [:root])