refactor(presence): execute the extinction_sec/anneal_sec withdrawal

docs/SPEC.md specified this removal, listed its parts, and ended "grep
for both names and expect no survivors". There were about forty.
docs/requirements.md meanwhile recorded both constants as Withdrawn and
"deleted rather than retained at zero", on the grounds that a field
naming a mechanism the pipeline no longer has is actively misleading.
Neither statement was true of the code: Config still carried
extinction_sec 57.4 and anneal_sec 35.5, --extinction and --anneal still
parsed, and SceneTrackerFunc still ran its keep-alive in both shipped
pipelines, announcing its timeout at every startup.

SceneTrackerFunc is replaced by FrameAnnotationFunc, which is stateless:
same ports, same output type, no keep-alive. Presence belongs to
TrackRegistry (AR-012), where a window is the extent of a track an actor
owned and ends at the last sighting (AR-013). The keep-alive answered
that question a second time and answered it worse, by re-opening exactly
the trailing cool-down AR-013 refuses.

Visible change: --verbosity standard's frames[].identified listed every
actor inside the keep-alive, including ones absent from the frame. It
now lists what was matched in that frame. Minimal and xray output is
untouched -- both were already built from registry claims and never
consulted this node. No schema bump: the published extraction block
reports track_extinction_sec, a different knob that bounds
re-association and never extends a claim.

TrackRegistry::Config::extinction_sec is renamed track_extinction_sec to
match the Config field feeding it, so the grep SPEC.md asks for now
returns nothing rather than one confusing false positive.

Two targets turned out to have been silently dead, both since the
AR-007/AR-008 tracker redesign, and both for the same reason -- they
construct FaceTrackerFunc from a Config alone, a signature that stopped
existing when association moved into probability space:

- scene_preview is fixed here. It now mirrors main.cpp's construction
  order exactly (matcher, then registry, then tracker) and wires the
  registry's claims into the sink, which it was not doing. DP-001 says
  modes are front-ends that must not fork pipeline logic; this one had
  forked it and then rotted.
- sae_kpn is not fixed. Restructuring the seam so the tracker can reach
  a calibration that only exists once the matcher is built is VR-011's
  rewrite, not a patch, and presence claims do not cross the seam at all
  today. It is now behind SAE_BUILD_KPN_BINDINGS=OFF with the reason
  recorded, so `cmake --build` succeeds and the breakage is attributed
  rather than rediscovered.

That second one is worth stating plainly: VR-002 ("replay drives the
real KPN nodes, not a reimplementation") is marked Done, and the module
that makes replay possible has not compiled for some time. The .so in a
stale build/ predates the change.

Python side: the two names are gone from optimize.py, replay.py and
run_holdout_all_models.py as Config keys. anneal_sec survives as
REPLAY_LOCAL_KEYS -- it still configures replay.py's own windowing,
which is a Python reimplementation that no longer matches the sink and
is documented as such. That divergence is VR-011's.

TRACES: AR-012, AR-013 | DP-001 | SR-002

CMakeLists.txt

@@ -322,11 +322,37 @@ nanobind_add_module(sae_embed src/python_bindings.cpp)
 target_link_libraries(sae_embed PRIVATE sae_gallery)
 
 # ── sae_kpn — Python module: run the real downstream nodes over dumped embeddings ─
-# Assembles face_tracker/identity_matcher/scene_tracker in a Python-driven KPN
+# Assembles face_tracker/identity_matcher/frame_annotation in a Python-driven KPN
 # network (KPN_BUILD_PYTHON is enabled per-TU inside the .cpp). Powers the
 # threshold-sweep optimizer in scripts/optimizer/.
-nanobind_add_module(sae_kpn src/kpn_bindings.cpp)
-target_link_libraries(sae_kpn PRIVATE sae_gallery)
+#
+# OFF by default, and this is a statement of fact rather than a preference: the
+# module HAS NOT COMPILED since the AR-007/AR-008 tracker redesign. FaceTrackerFunc
+# now requires a TrackRegistry and a calibration at construction, and the binding
+# still builds it from a Config alone. The .so in a stale build/ directory
+# predates that change.
+#
+# Fixing it is VR-011's job, not a patch: the tracker needs the calibration, the
+# calibration comes from the matcher, and the matcher is added to the network
+# afterwards -- so the seam has to be restructured, exactly as main.cpp already
+# is (matcher first, then registry, then tracker). Presence claims do not cross
+# the seam at all today, which is the other half of the same rewrite.
+#
+# Recorded as a switch rather than left as a build error so that `cmake --build`
+# succeeds and the breakage is attributed instead of rediscovered. Turning it on
+# reproduces the failure immediately, which is the point.
+#
+# TRACES: VR-011 | PR-002
+option(SAE_BUILD_KPN_BINDINGS
+       "Build the sae_kpn Python module (BROKEN pending VR-011)" OFF)
+if(SAE_BUILD_KPN_BINDINGS)
+    nanobind_add_module(sae_kpn src/kpn_bindings.cpp)
+    target_link_libraries(sae_kpn PRIVATE sae_gallery)
+else()
+    message(STATUS
+        "sae_kpn: SKIPPED (SAE_BUILD_KPN_BINDINGS=OFF). The Python replay "
+        "bindings do not compile against the post-AR-012 tracker; see VR-011.")
+endif()
 
 # ── sae_audio — Python module: the v1 audio signature (IR-004) ────────────────
 # Compiles audio_signature.cpp directly and links only FFmpeg, rather than