refactor(config): give the tuned constants a real provenance, and make them reachable

Two problems, both of which made a number look more settled than it is.

The provenance was a dead link. config.hpp cited
docs/rep4-optimizer-results.md for prob_threshold, extinction_sec,
anneal_sec and the expansion default. That file was renamed to
model-bakeoff.md and then rewritten; the comments were never repointed,
so the most consequential constant in the pipeline appeared to have no
source at all.

Following it up produced something worse than a broken link.
prob_threshold=0.754 comes from the ORIGINAL rep4 document (still
readable at `git show d340da7:docs/rep4-optimizer-results.md`). The
rewrite that replaced it 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". So 0.754 was fitted under
scoring that was later found wrong, the corrected sweep converged
elsewhere, and no corrected prob_threshold is recorded anywhere. The
comment now says that, along with the surviving document's own verdict
that the optimum "generalizes unevenly -- strong on 3 of 5 held-out
films, badly broken on 2".

Four constants were unreachable. ownership_logodds lived on
TrackRegistry::Config, and max_views/admit_below/rho_max on
EvidenceDiscounter::Config, which main built with the one-argument
constructor -- so nothing short of a recompile could move any of them.
rho_max's own comment defers to "the sweep (VR-007)" for where it
belongs, and that sweep could not reach it.

They now live in Config with CLI flags and are exposed to the replay
harness. ownership_logodds is worth singling out: below it a track makes
no presence claim at all, so it decides whether an actor is reported
rather than how confidently -- arguably the most consequential constant
after prob_threshold, and until now unswept and unsettable.

No behaviour change: every default is the value that was compiled in.

TRACES: AR-025, AR-017 | SR-002

scripts/optimizer/replay.py

@@ -277,7 +277,12 @@ def build_minimal(annotations, movie, fps, cfg) -> dict:
 # a stale entry here silently inert rather than loudly wrong.
 CFG_KEYS = ["detector_conf", "prob_threshold", "match_prior",
             "track_alpha", "track_min_iou", "track_assoc_min_prob",
-            "track_extinction_sec"]
+            "track_extinction_sec",
+            # AR-025 ownership and evidence accumulation. Newly reachable:
+            # these were in-class defaults no sweep could vary, which is why
+            # VR-007 never covered them despite rho_max deferring to it.
+            "ownership_logodds", "evidence_rho_max", "evidence_admit_below",
+            "evidence_max_views"]
 
 # Swept like a Config key but consumed entirely in Python, by build_minimal.
 # Kept separate so nobody has to guess which of these the pipeline actually