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.

CHANGELOG.md

@@ -10,6 +10,58 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 Nothing yet.
 
 
+## [0.7.0] — 2026-08-12
+
+### Added — `active:raw-html-link`, a click-required carrier class for raw HTML
+
+Raw HTML graded on activity alone: every active tag was HIGH. So the *same URL*
+was LOW as `[t](https://example.com/guide)` and HIGH as
+`<a href="https://example.com/guide">` — an asymmetry produced by syntax, not by
+affordance. Following an anchor needs a human, exactly like the markdown inline
+link that has been MEDIUM since 0.3.1.
+
+`<a>` and `<area>` now report as **`active:raw-html-link` at MEDIUM**. Everything
+a renderer fetches or executes unattended keeps `active:raw-html` at HIGH, and the
+event-handler test runs *first*, so `<a onclick=...>` is graded as the
+execute-class carrier it is rather than downgraded with the anchors.
+
+The URL-attribute branch deliberately stays on the HIGH side: a name outside the
+active set has unknown rendering, and `href` is not the only URL attribute it may
+carry. Grading `<Card src="...">` as a link would be reasoning, not measurement.
+
+**This is a new label, and labels are a contract surface consumers pin against.**
+A document that previously produced one `active:raw-html` finding may now produce
+two findings, one per carrier class.
+
+### Changed — a tag whose whole affordance is a URL it does not carry is inert
+
+`</a>`, `<Frame>`, `<video />` and `<img alt="...">` without `src` were active by
+*name* while naming no target at all. This is `<base />`'s argument from 0.6.0 —
+"attribute-less, therefore no affordance in any renderer" — applied to the rest of
+the name branch. The test is for the URL attribute's **presence**, not for a
+readable value: a value the parser cannot resolve keeps the tag active, mirroring
+the fail-secure gap `_url_attr_is_external` already leaves open.
+
+Every other member of the active name set does something a URL cannot describe —
+`<script>` executes its body, `<style>` restyles, `<form>` submits — and stays
+active with no attributes at all.
+
+### Changed — `active_tag_class` is the classification point; `is_active_tag` wraps it
+
+`docs/rawhtml-census.py` measures candidates by patching this symbol, and a
+boolean could only express a narrowing, never a regrade. Left as a boolean, every
+carrier candidate would have measured equal to PRODUCTION — silently, and in the
+direction that reads as "no change helps".
+
+### Known behaviour change
+
+**`count` drops on documents containing `</a>`.** Through 0.6.1 an end tag was
+active by name, so `count` ran roughly 1.6× the opening-tag total and a start/end
+pair counted 2. It is now the opening-tag total. The field's meaning did not
+change and the finding count is unaffected — the class still collapses to one
+finding per class per document.
+
+
 ## [0.6.1] — 2026-08-11
 
 ### Fixed — the zero-width check tested identity, so emoji-composed documents were hard-blocked