fix(pipeline): finish three changes that had only been half applied

Each of these was recorded as done and was done in one place out of two.

AR-011 -- the TransNetV2 dedup window. The derived window
(dedup_window_sec, median observed interval halved) reached scenes.json
and nothing else. SceneBoundaries, the path that actually feeds
is_scene_boundary to the tracker, kept the literal 0.04 s under a
comment claiming it "matches the dedup scenes.json applies, so the two
views agree". They did not agree. 0.04 is one frame at 25 fps and wider
than a frame at 30, so two cuts on consecutive frames merged into one
and the loss was invisible: the pipeline simply saw fewer boundaries.
The detector now supplies the window it derived.

AR-019 -- ownership. The register says ownership "comes from the
registry, not a second local tally". Both existed: promotion fired on a
local accepted-frame count and fell back to a local per-actor plurality
when the registry had not yet claimed the track. That fallback was
reachable in the live pipeline, not just in tests -- three accepted
frames arrive well before a posterior crosses the ownership threshold --
so in practice the plurality usually decided, and it could not see the
AR-025 correlation discounting it was meant to defer to. The tally is
gone; promotion now requires the registry's verdict, with the accepted
-frame count demoted to an explicit evidence floor.

AR-017 -- the route. DeadTrack carried belief but no route, and the sink
wrote the literal string "live", so a field the schema publishes could
not distinguish anything. AR-017's own verification asks for "deferred
and pooled routes distinguishable". Route is now an enum on the claim.
Only `live` occurs today; `deferred` exists so AR-020's pass has
somewhere to write instead of a serialisation change to make.

Also: TrackGallery::forget had no callers, under a comment asserting the
matcher called it "on a cut or track disappearance". The cut half was
true by another route; the disappearance half was not, so a track that
died quietly kept its diversity buffer until the next cut cleared
everything. Replaced with prune_dead against the registry's own
liveness, the same shape as the tracker's prune_boxes -- a second
opinion about which tracks exist is a second thing that can be wrong.

Removes dead logistic/logit helpers and fixes five TRACES tags that used
a comma where a pipe separates requirement types, which the gate had
been reporting as diagnostics.

TRACES: AR-011, AR-017, AR-019 | IR-002 | SR-002, SR-005

src/track_registry.hpp

@@ -44,12 +44,39 @@
 // A finished presence claim, emitted exactly once when a track is reaped or
 // flushed. Immutable by construction: it carries everything needed to justify
 // itself (AR-017), with no back-reference into registry state.
+/// TRACES: AR-017 | IR-002 | SR-002, SR-003
+/// How an actor came to be attached to a track.
+///
+/// AR-017 requires every presence claim to carry its identification route, and
+/// IR-002 publishes it per window. Until now the sink wrote the string "live"
+/// unconditionally, so the field existed but could not distinguish anything --
+/// and AR-017's own verification asks for "deferred and pooled routes
+/// distinguishable".
+///
+/// Only `live` occurs today. `deferred` is what AR-020's pass will set when it
+/// resolves a track that failed during streaming and was identified against the
+/// final expanded gallery; the value exists now so that pass has somewhere to
+/// write rather than a serialisation change to make.
+enum class Route {
+    live,       ///< identified while streaming, from accumulated per-frame evidence
+    deferred,   ///< resolved after EOF against the expanded gallery (AR-020)
+};
+
+inline const char* route_name(Route r) {
+    switch (r) {
+        case Route::deferred: return "deferred";
+        case Route::live:     break;
+    }
+    return "live";
+}
+
 struct DeadTrack {
     int    track_id{-1};
     double first_seen{0.0};
     double last_seen{0.0};   ///< always the last sighting, never the death time
     int    actor_idx{-1};    ///< -1 when the track was never owned
     float  belief{0.0f};     ///< accumulated posterior for actor_idx
+    Route  route{Route::live}; ///< how the actor was attached (AR-017)
     int    observations{0};    ///< evidence updates that landed on this track
     float  effective_obs{0.f}; ///< sum of discounted weights — the evidence that counted
 };
@@ -215,6 +242,15 @@ public:
     // ── Diagnostics ──────────────────────────────────────────────────────────
     // These measure how often tracking is silently wrong, which nothing in the
     // pipeline currently reveals.
+    /// Whether the registry still holds this track. The authority on which
+    /// tracks exist, so annotating structures elsewhere (spatial boxes in the
+    /// tracker, diversity buffers in the expansion store) can prune against it
+    /// rather than keeping a second opinion.
+    bool is_live(int track_id) const {
+        std::lock_guard g(mu_);
+        return tracks_.count(track_id) != 0;
+    }
+
     int dropped_votes()   const { std::lock_guard g(mu_); return dropped_votes_; }
     int belief_swaps()    const { std::lock_guard g(mu_); return belief_swaps_; }
     int actor_conflicts() const { std::lock_guard g(mu_); return actor_conflicts_; }
@@ -340,17 +376,6 @@ private:
         for (int i = 0; i < 512; ++i) t.mean[i] = static_cast<float>(t.mean[i] / norm);
     }
 
-    static float logistic(float z) {
-        return z >= 0 ? 1.f / (1.f + std::exp(-z))
-                      : std::exp(z) / (1.f + std::exp(z));
-    }
-
-    static float logit(float p) {
-        const float eps = 1e-6f;
-        p = std::min(1.f - eps, std::max(eps, p));
-        return std::log(p / (1.f - p));
-    }
-
     Config                cfg_;
     EvidenceDiscounter    discounter_;
     mutable std::mutex    mu_;