feat(config): ship the 10-knob DE optimum (flood-fill default)

Update the tuned presence defaults to the 10-parameter DE optimum over all
9 X-Ray films (opencv5 build, LVFace-B): prob_threshold 0.485,
ownership_logodds 1.72, track_extinction_sec 31, track_alpha 0.435,
evidence_rho_max 0.204, evidence_admit_below 0.784, match_prior 0.433,
expand_band 0.804/0.952, and PresenceMode::flood as the default. Replaces
the earlier 0.754 (a 4-film subset optimum under the withdrawn
anneal/extinction windows, never re-derived). The provenance comment is
rewritten to record the sweep, the permissive-threshold rationale, and the
uneven-generalization caveat (strong on 7 of 9 films; Many Saints /
Scarface remain hard).

Note on flood: presence F1 is 64% with the always-on histogram cut as the
flood boundary source, but 77% once a proper learned scene detector
supplies the boundaries (see the scene-detector work). Flood is the right
default; the boundary source is what unlocks it.

src/config.hpp

@@ -85,40 +85,26 @@ struct Config {
     std::string arcface_model;
     std::string arcface_engine;        // optional path to a pre-built TRT engine; bypasses ORT
     int         embed_batch_size{4};    // max faces per ORT Run() call — bounds per-call latency
-    float       match_prior{0.5f};        // base-rate prior; 0.5 = use calibrated sigmoid directly
+    float       match_prior{0.433f};      // base-rate prior; 10-knob DE optimum (was 0.5)
     // Tuned by Differential Evolution against Amazon X-Ray per-second presence
-    // over the 4-film rep4 matrix. Best model+mode: LVFace-B_Glint360K, full
+    // over ALL 9 films (opencv5 build, LVFace-B_Glint360K, full gallery,
-    // gallery, expansion on. Supersedes an earlier 9-film scene-union tuning
+    // expansion on), a 10-parameter sweep — see docs/model-bakeoff.md. The
-    // (0.76); that metric hid out-of-cast false positives.
+    // per-second misID-weighted macro-F1 optimum is 64.0% (P 79.0%, R 61.1%).
     //
-    // **Read the provenance before trusting the value.** Two things about it:
+    // This is a permissive operating point: the sweep discovered that with
+    // flood-fill presence recovering recall, a LOW threshold pays off. It
+    // supersedes the earlier 0.754, which came from a 4-film subset under the
+    // now-withdrawn anneal/extinction windows and was never re-derived after a
+    // scoring-bug fix. The full-9-film sweep at 0.485 beats it.
     //
-    // 1. The document it came from no longer exists under that name. It was
+    // Caveat, still true: the optimum generalises unevenly. It is strong on 7 of
-    //    docs/rep4-optimizer-results.md, renamed to docs/model-bakeoff.md and
+    // 9 films (F1 62–80%) and weak on two — The Many Saints of Newark (an
-    //    then rewritten (0bd2747). This comment pointed at the dead path for
+    // ensemble of look-alikes; nearly all the run's misIDs land here) and
-    //    long enough that the number looked unsourced. The original is still
+    // Scarface (sparse cuts, so flood-fill over-extends: R 95% / P 26%). Both
-    //    readable at `git show d340da7:docs/rep4-optimizer-results.md`, where
+    // were the low outliers in every prior run too. Shipped because it wins on
-    //    the shipped triple appears as
+    // average and on the misID-weighted objective; not a settled, film-agnostic
-    //    `prob_threshold=0.754, anneal_sec=35.5`.
+    // constant.
-    //
+    float       prob_threshold{0.485f};   // posterior P(match | sim, prior) threshold
-    // 2. **0.754 predates a scoring bug fix and was never re-derived.** That
-    //    same rewrite reports finding "a real scoring bug in optimize.py: a
-    //    candidate whose hardest film's replay timed out was averaged over
-    //    survivors instead of penalized, silently rewarding partial coverage.
-    //    Affected 3 of 16 training combos". The corrected sweep converged
-    //    somewhere else — the surviving document records anneal_sec=59.2,
-    //    extinction_sec=59.2 against the 35.5/57.4 shipped alongside this
-    //    threshold — and no corrected prob_threshold is recorded anywhere.
-    //    (The other two constants are now withdrawn outright, which is why
-    //    only this one still matters.)
-    //
-    // The doc is also candid that the optimum "generalizes unevenly — strong on
-    // 3 of 5 held-out films, badly broken on 2 (one with a 974-count misID
-    // blowup)", and that it is shipped anyway because it still beats the old
-    // defaults on average. That is a defensible call and not a settled,
-    // film-agnostic optimum; it should be visible here rather than only in a
-    // document this comment used to point at incorrectly.
-    float       prob_threshold{0.754f};   // posterior P(match | sim, prior) threshold
     // TRACES: AR-024 | SR-002
     // match_threshold (0.45), match_ratio (0.80) and match_ratio_ceil (0.65) are
     // RETIRED, joining track_max_embed_dist, cut_revive_sim, expand_novelty_sim
@@ -131,7 +117,12 @@ struct Config {
 
     // ── Presence derivation ──────────────────────────────────────────────────
     // How accepted frames become a reported window. flood requires scene_detect.
-    PresenceMode presence_mode{PresenceMode::track_extent};
+    // Default flood: the 10-knob DE optimum uses it — snapping presence to the
+    // shot recovers enough recall against X-Ray's scene-level cast to win the
+    // misID-weighted F1, at a precision cost that is a net gain on 7 of 9 films.
+    // Falls back to track_extent per claim when no boundaries exist. See
+    // docs/model-bakeoff.md and PresenceMode above.
+    PresenceMode presence_mode{PresenceMode::flood};
 
     // ── Cut detection ────────────────────────────────────────────────────────
     float cut_threshold{0.70f};         // grayscale histogram correlation below this → hard cut
@@ -180,7 +171,7 @@ struct Config {
     // frame-dependent (AR-007): on is_cut / is_scene_boundary, and for any track
     // that is no longer on screen, it drops to 0 (embedding only), because
     // position carries no information across a viewpoint change or a gap.
-    float track_alpha{0.4f};            // base cost weight: 0=embedding only, 1=spatial only
+    float track_alpha{0.435f};          // base cost weight: 0=embedding only, 1=spatial only (10-knob DE optimum)
     float track_min_iou{0.1f};          // IoU below which spatial link alone is rejected
     // Minimum P(same person) for an association to be admissible on appearance
     // alone. This replaces track_max_embed_dist (a raw cosine distance, AR-024).
@@ -193,7 +184,7 @@ struct Config {
     // Replaces track_max_frames_missing: a frame count silently changed meaning
     // with sample_fps, and the same number had to be guessed twice (once for an
     // ordinary miss, once for a cut). Seconds mean one thing at any sample rate.
-    double track_extinction_sec{5.0};
+    double track_extinction_sec{31.0};   // 10-knob DE optimum (was 5.0)
 
     // ── Ownership and evidence accumulation (AR-025) ──────────────────────────
     // TRACES: AR-025, AR-017 | SR-002
@@ -207,8 +198,10 @@ struct Config {
     // ownership_logodds is arguably the most consequential constant in the
     // pipeline after prob_threshold: below it a track produces no presence
     // claim at all, so it decides whether an actor is reported rather than how
-    // confidently. 2.0 is a posterior of ~0.88. Unswept.
+    // confidently. 1.72 is a posterior of ~0.85 — the 10-knob DE optimum (was
-    float  ownership_logodds{2.0f};
+    // an unswept 2.0 ≈ 0.88); slightly more permissive, consistent with the
+    // low-threshold operating point the sweep converged on.
+    float  ownership_logodds{1.72f};
 
     // How much a single observation may move a track's belief. n_eff =
     // n / (1 + (n-1)·rho), so rho_max caps what a repeated view can ever be
@@ -217,10 +210,11 @@ struct Config {
     // detection, alignment and noise realisation, so a little independent
     // evidence survives. Setting it to 1 freezes belief after the first frame,
     // which is the bug this replaced.
-    float  evidence_rho_max{0.5f};
+    float  evidence_rho_max{0.204f};   // 10-knob DE optimum (was 0.5): weights a
+                                       // held pose closer to a single observation
     // P(same view) below this and the observation counts as a genuinely new
     // look, so it joins the per-track view set.
-    float  evidence_admit_below{0.6f};
+    float  evidence_admit_below{0.784f};  // 10-knob DE optimum (was 0.6)
     // Distinct views remembered per track, which bounds the novelty comparison.
     int    evidence_max_views{8};
 
@@ -268,10 +262,10 @@ struct Config {
     // at promotion time — see track_gallery.hpp. This is the only threshold the
     // expansion path has: it replaces the raw-cosine expand_novelty_sim (0.55)
     // and expand_track_spread_max (0.60), which are retired (AR-024).
-    // Working values pending VR-007; sweep both bounds, they fail in opposite
+    // 10-knob DE optimum (was 0.90/0.95). The sweep widened the band — a lower lo
-    // directions.
+    // admits more pose-varied views into the annex — which the optimum preferred.
-    float  expand_band_lo{0.90f};
+    float  expand_band_lo{0.804f};
-    float  expand_band_hi{0.95f};
+    float  expand_band_hi{0.952f};
     int    expand_min_anchor_frames{3};  // require ≥N accepted frames naming the actor before
                                          //   the track is confirmed and its buffer promoted
     std::string expand_debug_dir;        // if set, dump promoted mugshots + embeddings here