feat(active): report a run of images whose order carries a value

Session 6 of the 2026 threat plan (attack row 3): A05 output was red.
CamoLeak renders a secret as one image per character from a URL alphabet;
each URL is ordinary, so each image graded LOW and the gate WARNed.

- active:markdown-image-sequence (MEDIUM): at least 4 ordinary external
  images, inline or reference-style, on one URL template whose varying
  tokens are 2 chars or fewer, or digit runs. Digits that count up in
  document order are a counter and carry nothing. The per-image grade is
  unchanged; the finding sits beside it.
- Accepted twins (flag tables, figures 1a/1b) go to review; measured
  evasions (word dictionary, 3-char symbols, counter increments, run of 3,
  a template per symbol) are in LIMITATIONS.

Guard rule before/after: FP 106/198, 196/2918, 108/389 identical. Those
corpora hold no external markdown image, so the rule was also run on 577
package READMEs (312 with external images): 0 firings at run lengths 3-8.
OKF import 47/31 identical. Matrix 140/140, ReDoS 163 patterns 0 flagged,
suite 1179 passed + 5 xfailed. Row 3: 13 caught, 1 gap, 5 open.

tests/test_docs_measurement_scripts.py

@@ -272,13 +272,13 @@ def test_redos_sweep_floor_and_flag_match_the_published_numbers():
     assert "2.6 flag threshold" in text
 
 
-def test_redos_sweep_collector_covers_161_patterns_across_11_tables():
-    # The count docs/LIMITATIONS.md carries as "all 161 compiled patterns across
+def test_redos_sweep_collector_covers_163_patterns_across_11_tables():
+    # The count docs/LIMITATIONS.md carries as "all 163 compiled patterns across
     # all eleven regex-bearing modules". A pattern added or removed in `src/`
     # without re-measuring would drift the doc's claim silently otherwise.
     assert len(redos_sweep.TABLES) == 11
     total = sum(len(collect()) for collect in redos_sweep.TABLES.values())
-    assert total == 161
+    assert total == 163
 
 
 # --- both scripts: the argument-less contract --------------------------------