fix(sanitize,okf,active_content): three quadratic patterns, two on the input path

The generalised sweep found what 0.3.2's hand-written rows missed. All three are
the documented class -- a run in front of a required literal that never arrives,
so every start position rescans the tail -- and all three are worse than the
0.3.3 findings, because `sanitize`, `neutralize`, `scan_active_content` and the
okf link graph apply NO input cap. `scan_lexicon`/`scan_output` are the only
entry points that do, so there is no ceiling to extrapolate to.

  sanitize._HTML_COMMENT_RE   `<!--`*100_000        20.1s, exponent 1.96-2.14
  active_content.URL_IN_TEXT_RE  `<a `+`A`*100_000  12.99s / 14.9s, exponent ~2.0
  okf._MD_LINK_RE             `[`*100_000            7.1s, exponent 1.99-2.05

Each fix is the one the pattern's own shape allows, not a copied choice:

  - The comment stripper drops the regex for `str.find`. Excluding `<` would lose
    every comment containing markup; bounding the run would be a carrier bypass
    of the exact construct the stripper exists to remove.
  - `URL_IN_TEXT_RE` bounds its scheme run to an RFC 3986 scheme (`{0,63}`).
    Bounding is safe *here* only because it is a defanger inside a tag already
    flagged `active:raw-html`. A lookbehind was measured too and rejected: it
    drops `-http://evil.com`, a one-character evasion. Bounded: 0.185s at 1M.
  - `_MD_LINK_RE` excludes `[`, matching `active_content.MD_LINK_RE` exactly,
    including the nested-label trade already documented there.

`sanitize` claimed "no catastrophic backtracking" in a comment; that claim was
wrong in the same way `output`'s was before 0.3.2, and is corrected in place.

676 tests (+10), coverage 128/128 + 6/6 gaps, sweep clean across 150 patterns.
The okf destination run gets no row: `[^)\s]+` cannot fail, so a row for it
could never go red.

tests/test_neutralize.py

@@ -11,6 +11,8 @@ empty report; only active-content constructs are ever rewritten. Mutation lives
 here, kept separate from the report-only output gate (design principles 3 & 4).
 The transform is pure ``text -> (defanged_text, report)`` — no I/O, no globals.
 """
+import time
+
 from llm_ingestion_guard.neutralize import neutralize
 from llm_ingestion_guard.report import Severity, Source
 
@@ -139,3 +141,23 @@ def test_prose_with_lone_brackets_and_angles_is_identical():
     result = neutralize(text)
     assert result.text == text
     assert result.report.found is False
+
+
+# --- self-safety (OWASP LLM10): the long-attribute arm -----------------------
+# Second call site of the same defect pinned in test_active_content.py: the
+# defanger runs `URL_IN_TEXT_RE` over each active tag's body. 14.9s at 100_000
+# chars, exponent 1.91-2.22. `neutralize` applies no input cap either.
+_ATTR_REDOS_N = 100_000
+
+
+def test_crafted_long_attribute_tag_stays_bounded():
+    payload = "<a " + "A" * _ATTR_REDOS_N + ">"
+    start = time.monotonic()
+    neutralize(payload)
+    assert time.monotonic() - start < 2.0
+
+
+def test_url_defanging_inside_a_tag_survives_the_redos_fix():
+    result = neutralize("<a href=-http://evil.com>x</a>")
+    assert "hxxp" in result.text
+    assert "http://evil.com" not in result.text