feat(active-content): raw HTML graded on carrier, and a tag naming no target is inert

Two changes that had to ship together, because they co-occur.

`active:raw-html-link` (MEDIUM) splits the click-required carriers out of
`active:raw-html`. The same URL was LOW as `[t](url)` and HIGH as
`<a href="url">` — an asymmetry produced by syntax, not by affordance, on a
carrier the markdown path has graded MEDIUM since 0.3.1. The event-handler test
runs first, so `<a onclick=...>` stays HIGH. The url-attribute branch stays HIGH
too: a name outside the active set has unknown rendering, and grading
`<Card src=...>` as a link would be reasoning rather than measurement.

The no-URL narrowing makes `</a>`, `<Frame>`, `<video />` and `<img alt=...>`
without `src` inert — `<base />`'s argument from 0.6.0 applied to the rest of the
name branch. It tests for the URL attribute's PRESENCE, not for a readable value,
so the fail-secure gap `_url_attr_is_external` leaves open is not reopened here.

WHY TOGETHER: the narrowing strips a document's `</a>`/`<Frame>` and what remains
is the `<a href=...>` the split grades down, so each alone leaves the document
blocked by the other's residue.

`active_tag_class` is now the classification point and `is_active_tag` wraps it.
The census patches the former: a boolean could only express a narrowing, never a
regrade, so every carrier candidate would have measured equal to PRODUCTION —
silently, and in the direction that reads as "no change helps".

TWO COSTS, BOTH RECORDED RATHER THAN GLOSSED:

- The split TIGHTENS the trusted tier. One finding becomes two, and >=2 findings
  at MEDIUM+ trip the compound overlay, so a document carrying both an `<img src>`
  and an `<a href>` goes WARN -> quarantine_review on PRESET_TRUSTED_SOURCE. On
  that preset it is the only direction the split can move anything. The census
  now reports a TIGHTENS column on both trust tiers against the previously
  shipped row — "frees N" without "tightens M" is a one-sided number.
- `count` drops on documents containing `</a>`, a published field moving under a
  meaning that did not change.

MEASURED: reference-corpus (389) 54 -> 53 fail_secure, tightens 0/0, and the
census `PRODUCTION` row equals its `C1 + D` candidate row for row. The census
also reproduces 133/3/13/108/25 exactly, so it is calibrated against every
published historical number. The two wiki corpora are NOT yet re-measured; the
tree says so explicitly in the docstring, LIMITATIONS and CHANGELOG rather than
carrying probe numbers as fact.

791 tests (was 759), coverage 129/129, 6/6 documented gaps holding. Version
bumped to 0.7.0 across every surface; no tag is set until the measurement lands.

README.md

@@ -2,7 +2,7 @@
 
 Write-time defensive layer for Python pipelines that persist LLM output: sanitize, fence, tool-less quarantined transform, capability isolation, scan before persist, fail-secure.
 
-![Version](https://img.shields.io/badge/version-0.6.1-blue)
+![Version](https://img.shields.io/badge/version-0.7.0-blue)
 ![Status](https://img.shields.io/badge/status-alpha-orange)
 ![Python](https://img.shields.io/badge/python-3.10%2B-purple)
 ![License](https://img.shields.io/badge/license-MIT-lightgrey)
@@ -33,7 +33,7 @@ at write time, never assumed from the format. Any pipeline ingesting external da
 into an agent-read store has this shape; an OKF wiki is its canonical form — which
 is why the guard ships a first-class OKF adapter (below).
 
-**Status:** `v0.6`, alpha. The stdlib-only core — its detector, contract, and
+**Status:** `v0.7`, alpha. The stdlib-only core — its detector, contract, and
 OKF-adapter modules plus the top-level wiring — is built and tested, exercised by
 an end-to-end showcase and adversarial + false-positive corpora. The public API
 may still change. There are real limitations, stated plainly below; read them.
@@ -43,7 +43,7 @@ may still change. There are real limitations, stated plainly below; read them.
 Not on PyPI. The guard is distributed from its Forgejo origin — pin a release tag:
 
 ```bash
-pip install "llm-ingestion-guard @ git+https://git.fromaitochitta.com/open/llm-ingestion-pipeline-security.git@v0.6.1"
+pip install "llm-ingestion-guard @ git+https://git.fromaitochitta.com/open/llm-ingestion-pipeline-security.git@v0.7.0"
 ```
 
 The `open/` mirror is anonymously readable, so CI needs no deploy key, token, or
@@ -164,7 +164,7 @@ driven by a **live payload** in the coverage matrix — run it to watch all 134
 in your own environment:
 
 ```bash
-python -m llm_ingestion_guard.coverage    # 128/128 classes; exit 0 = all as documented
+python -m llm_ingestion_guard.coverage    # 129/129 classes; exit 0 = all as documented
 ```
 
 | Anchor | Attack classes it stops (representative) |
@@ -246,7 +246,7 @@ a green scan means safe content. The highest-impact items:
   two of the three corpora are living, so the cells are not rewritten in place.
   Method and before/after: [`docs/rawhtml-census.py`](docs/rawhtml-census.py).
 
-**Full list — 34 items, each with the mechanism, plus the out-of-scope boundary:**
+**Full list — 35 items, each with the mechanism, plus the out-of-scope boundary:**
 [`docs/LIMITATIONS.md`](docs/LIMITATIONS.md). Several carry field measurements from
 consumer corpora, including the false positives the URL-shape rule actually produces.