docs(register): make the status column describe the code

Eleven rows corrected, in both directions.

Overstated: AR-011 (the derived dedup window reached scenes.json only),
AR-017 (route was a literal), AR-019 (the local plurality tally was
still deciding), AR-024 (its "static check" enforcement did not exist),
DP-001 (scene_preview had forked and stopped compiling), VR-002 (the
Python replay bindings have not compiled since the tracker redesign, and
the fixtures it calls committed are gitignored registry artifacts).

Understated: VR-010 was marked Planned while five VR-010 tags sat in the
code implementing it.

Rescoped: VR-007 now names the four AR-025 constants it was already
being deferred to for, and which no sweep could reach until this pass.

The Withdrawn note gets the longest correction, because it asserted a
removal that had not happened and nothing could have caught that: the
gate reads tags, and a withdrawn requirement has no tag to be orphaned.
The general form is now written down there -- a status column is a
claim, and the only claims this project checks automatically are the
ones a test or a static check makes. Four of the rows above are the same
pattern: recorded as done, and done in one place out of two.

New: VR-016, a cadence study for cut_threshold. It is the one always-on
signal with no recorded provenance, and its input rate depends on an
unrelated flag -- with --scene-detect off, camera_pos compares frames a
full second apart at the default sample_fps, and with it on, native-rate
frames. Same constant, two meanings, and is_cut drives track_alpha to 0
and clears every expansion buffer.

Also stops check_raw_cosine.py inflating its own metric: the extractor
scans scripts/, so the tool's prose describing the exception tag was
counted as four recorded exceptions. The count now reads 1, which is the
number of real ones.

TRACES: AR-011, AR-017, AR-019, AR-024, AR-025 | DP-001, DP-007 | IR-004 | VR-002, VR-007, VR-010, VR-016

scripts/ci/check_raw_cosine.py

@@ -18,8 +18,13 @@ worse than one with a stated scope:
     (a) have its result consumed immediately by a calibration -- the call is
         textually wrapped in `cal_(...)`, `calibrate_(...)`, `.probability(...)`
         or similar; or
-    (b) sit under an `EXCEPTION: AR-024 <reason>` comment within
-        EXCEPTION_SCOPE_LINES above it.
+    (b) sit under an exception comment -- the token is `EXCEPTION:` followed by
+        `AR-024` and a reason -- within EXCEPTION_SCOPE_LINES above it.
+
+Note that this file deliberately never spells that token out. The traceability
+extractor scans scripts/ as source, so prose here describing the tag would be
+counted as recorded exceptions; four of them were, until this was noticed. The
+same trap the shared config warns about for the vendored parser tests.
 
   Anything else is a defect, per CLAUDE.md: "treat any bare cosine comparison in
   the code as a defect to be fixed".
@@ -45,7 +50,7 @@ import pathlib
 import re
 import sys
 
-# How far above a use an `EXCEPTION: AR-024` tag may sit and still cover it.
+# How far above a use an exception tag may sit and still cover it.
 # Generous, because the house style puts a paragraph of reasoning between the
 # tag and the code -- but bounded, so a tag cannot silently cover a whole file.
 EXCEPTION_SCOPE_LINES = 25
@@ -80,7 +85,7 @@ CALIBRATED = re.compile(
     r"cosine_similarity\s*\("
 )
 
-EXCEPTION_TAG = re.compile(r"EXCEPTION:\s*AR-024\b(.*)")
+EXCEPTION_TAG = re.compile(r"EXCEPT" + r"ION:\s*AR-" + r"024\b(.*)")
 
 # The function's own definition is not a use of it.
 DEFINITION = re.compile(r"^\s*(?:inline\s+|static\s+|constexpr\s+)*float\s+"
@@ -109,7 +114,7 @@ def iter_sources(root: pathlib.Path, roots):
 
 
 def covering_exception(lines, idx):
-    """Return the reason text of an EXCEPTION: AR-024 tag covering line `idx`."""
+    """Return the reason text of an exception tag covering line `idx`."""
     lo = max(0, idx - EXCEPTION_SCOPE_LINES)
     for j in range(idx, lo - 1, -1):
         m = EXCEPTION_TAG.search(lines[j])
@@ -208,7 +213,7 @@ def main():
         print("\nEither route it through the calibration, or, if the use is")
         print("genuinely about the metric space rather than about a decision,")
         print("record it:")
-        print("      // EXCEPTION: AR-024 <why this one is not a decision>")
+        print("      // " + "EXCEPT" + "ION: AR-" + "024 <why this one is not a decision>")
         print("and add a row to CLAUDE.md's agreed-exceptions table.")
         return 1